"""Module support for converting to/from ParmEd objects."""
import warnings
import numpy as np
import sympy as sym
import unyt as u
from sympy.parsing.sympy_parser import parse_expr
import gmso
from gmso.core.element import (
element_by_atom_type,
element_by_name,
element_by_symbol,
)
from gmso.utils.io import has_parmed, import_
if has_parmed:
pmd = import_("parmed")
[docs]def from_parmed(structure, refer_type=True):
"""Convert a parmed.Structure to a gmso.Topology.
Convert a parametrized or un-parametrized parmed.Structure object to a topology.Topology.
Specifically, this method maps Structure to Topology and Atom to Site.
At this point, this method can only convert AtomType, BondType and AngleType.
Conversion of DihedralType will be implement in the near future.
Parameters
----------
structure : parmed.Structure
parmed.Structure instance that need to be converted.
refer_type : bool, optional, default=True
Whether or not to transfer AtomType, BondType, AngleType,
and DihedralType information
Returns
-------
top : gmso.Topology
"""
msg = "Provided argument is not a Parmed Structure"
assert isinstance(structure, pmd.Structure), msg
top = gmso.Topology(name=structure.title)
site_map = dict()
if np.all(structure.box):
# This is if we choose for topology to have abox
top.box = gmso.Box(
(structure.box[0:3] * u.angstrom).in_units(u.nm),
angles=u.degree * structure.box[3:6],
)
# TO DO: come up with a solution to deal with partially parametrized
# Parmed Structure
# Old code:
# simple check if our pmd.Structure is fully parametrized
# is_parametrized = True if (isinstance(structure.atoms[i].atom_type,
# pmd.AtomType) for i in range(len(structure.atoms))) else False
# Consolidate parmed atomtypes and relate topology atomtypes
if refer_type:
pmd_top_atomtypes = _atom_types_from_pmd(structure)
# Consolidate parmed bondtypes and relate to topology bondtypes
bond_types_map = _get_types_map(structure, "bonds")
pmd_top_bondtypes = _bond_types_from_pmd(
structure, bond_types_members_map=bond_types_map
)
# Consolidate parmed angletypes and relate to topology angletypes
angle_types_map = _get_types_map(structure, "angles")
pmd_top_angletypes = _angle_types_from_pmd(
structure, angle_types_member_map=angle_types_map
)
# Consolidate parmed dihedraltypes and relate to topology dihedraltypes
dihedral_types_map = _get_types_map(structure, "dihedrals")
dihedral_types_map.update(_get_types_map(structure, "rb_torsions"))
pmd_top_dihedraltypes = _dihedral_types_from_pmd(
structure, dihedral_types_member_map=dihedral_types_map
)
subtops = list()
for residue in structure.residues:
subtop_name = ("{}[{}]").format(residue.name, residue.idx)
subtops.append(gmso.SubTopology(name=subtop_name, parent=top))
for atom in residue.atoms:
if refer_type and isinstance(atom.atom_type, pmd.AtomType):
site = gmso.Atom(
name=atom.name,
charge=atom.charge * u.elementary_charge,
position=(
[atom.xx, atom.xy, atom.xz] * u.angstrom
).in_units(u.nm),
atom_type=pmd_top_atomtypes[atom.atom_type],
)
else:
site = gmso.Atom(
name=atom.name,
charge=atom.charge * u.elementary_charge,
position=(
[atom.xx, atom.xy, atom.xz] * u.angstrom
).in_units(u.nm),
atom_type=None,
)
site_map[atom] = site
subtops[-1].add_site(site)
top.add_subtopology(subtops[-1])
for bond in structure.bonds:
# Generate bond parameters for BondType that gets passed
# to Bond
if refer_type and isinstance(bond.type, pmd.BondType):
top_connection = gmso.Bond(
connection_members=[site_map[bond.atom1], site_map[bond.atom2]],
bond_type=pmd_top_bondtypes[bond.type],
)
# No bond parameters, make Connection with no connection_type
else:
top_connection = gmso.Bond(
connection_members=[site_map[bond.atom1], site_map[bond.atom2]],
bond_type=None,
)
top.add_connection(top_connection, update_types=False)
top.update_topology()
for angle in structure.angles:
# Generate angle parameters for AngleType that gets passed
# to Angle
if refer_type and isinstance(angle.type, pmd.AngleType):
top_connection = gmso.Angle(
connection_members=[
site_map[angle.atom1],
site_map[angle.atom2],
site_map[angle.atom3],
],
angle_type=pmd_top_angletypes[angle.type],
)
# No bond parameters, make Connection with no connection_type
else:
top_connection = gmso.Angle(
connection_members=[
site_map[angle.atom1],
site_map[angle.atom2],
site_map[angle.atom3],
],
angle_type=None,
)
top.add_connection(top_connection, update_types=False)
for dihedral in structure.dihedrals:
# Generate dihedral parameters for DihedralType that gets passed
# to Dihedral
# These all follow periodic torsions functions
# (even if they are improper dihedrals)
# Which are the default expression in top.DihedralType
# These periodic torsion dihedrals get stored in top.dihedrals
if dihedral.improper:
warnings.warn(
"ParmEd improper dihedral {} ".format(dihedral)
+ "following periodic torsion "
+ "expression detected, currently accounted for as "
+ "topology.Dihedral with a periodic torsion expression"
)
if refer_type and isinstance(dihedral.type, pmd.DihedralType):
top_connection = gmso.Dihedral(
connection_members=[
site_map[dihedral.atom1],
site_map[dihedral.atom2],
site_map[dihedral.atom3],
site_map[dihedral.atom4],
],
dihedral_type=pmd_top_dihedraltypes[dihedral.type],
)
# No bond parameters, make Connection with no connection_type
else:
top_connection = gmso.Dihedral(
connection_members=[
site_map[dihedral.atom1],
site_map[dihedral.atom2],
site_map[dihedral.atom3],
site_map[dihedral.atom4],
],
dihedral_type=None,
)
top.add_connection(top_connection, update_types=False)
for rb_torsion in structure.rb_torsions:
# Generate dihedral parameters for DihedralType that gets passed
# to Dihedral
# These all follow RB torsion functions
# These RB torsion dihedrals get stored in top.dihedrals
if rb_torsion.improper:
warnings.warn(
"ParmEd improper dihedral {} ".format(rb_torsion)
+ "following RB torsion "
+ "expression detected, currently accounted for as "
+ "topology.Dihedral with a RB torsion expression"
)
if refer_type and isinstance(rb_torsion.type, pmd.RBTorsionType):
top_connection = gmso.Dihedral(
connection_members=[
site_map[rb_torsion.atom1],
site_map[rb_torsion.atom2],
site_map[rb_torsion.atom3],
site_map[rb_torsion.atom4],
],
dihedral_type=pmd_top_dihedraltypes[rb_torsion.type],
)
# No bond parameters, make Connection with no connection_type
else:
top_connection = gmso.Dihedral(
connection_members=[
site_map[rb_torsion.atom1],
site_map[rb_torsion.atom2],
site_map[rb_torsion.atom3],
site_map[rb_torsion.atom4],
],
dihedral_type=None,
)
top.add_connection(top_connection, update_types=False)
top.update_topology()
top.combining_rule = structure.combining_rule
return top
def _atom_types_from_pmd(structure):
"""Convert ParmEd atomtypes to GMSO AtomType.
This function take in a Parmed Structure, iterate through its
atom's atom_type, create a corresponding GMSO.AtomType, and
finally return a dictionary containing all pairs of pmd.AtomType
and GMSO.AtomType
Parameter
----------
structure: pmd.Structure
Parmed Structure that needed to be converted.
Return
------
pmd_top_atomtypes : dict
A dictionary linking a pmd.AtomType object to its
corresponding GMSO.AtomType object.
"""
unique_atom_types = set()
for atom in structure.atoms:
if isinstance(atom.atom_type, pmd.AtomType):
unique_atom_types.add(atom.atom_type)
unique_atom_types = list(unique_atom_types)
pmd_top_atomtypes = {}
for atom_type in unique_atom_types:
top_atomtype = gmso.AtomType(
name=atom_type.name,
charge=atom_type.charge * u.elementary_charge,
parameters={
"sigma": atom_type.sigma * u.angstrom,
"epsilon": atom_type.epsilon * u.Unit("kcal / mol"),
},
mass=atom_type.mass,
)
pmd_top_atomtypes[atom_type] = top_atomtype
return pmd_top_atomtypes
def _bond_types_from_pmd(structure, bond_types_members_map=None):
"""Convert ParmEd bondtypes to GMSO BondType.
This function takes in a Parmed Structure, iterate through its
bond_types, create a corresponding GMSO.BondType, and finally
return a dictionary containing all pairs of pmd.BondType
and GMSO.BondType
Parameters
----------
structure: pmd.Structure
Parmed Structure that needed to be converted.
bond_types_members_map: optional, dict, default=None
The member types (atomtype string) for each atom associated with the bond_types the structure
Returns
-------
pmd_top_bondtypes : dict
A dictionary linking a pmd.BondType object to its
corresponding GMSO.BondType object.
"""
pmd_top_bondtypes = dict()
bond_types_members_map = _assert_dict(
bond_types_members_map, "bond_types_members_map"
)
for btype in structure.bond_types:
bond_params = {
"k": (2 * btype.k * u.Unit("kcal / (angstrom**2 * mol)")),
"r_eq": btype.req * u.angstrom,
}
member_types = bond_types_members_map.get(id(btype))
top_bondtype = gmso.BondType(
parameters=bond_params, member_types=member_types
)
pmd_top_bondtypes[btype] = top_bondtype
return pmd_top_bondtypes
def _angle_types_from_pmd(structure, angle_types_member_map=None):
"""Convert ParmEd angle types to GMSO AngleType.
This function takes in a Parmed Structure, iterates through its
angle_types, create a corresponding GMSO.AngleType, and finally
return a dictionary containing all pairs of pmd.AngleType
and GMSO.AngleType
Parameters
----------
structure: pmd.Structure
Parmed Structure that needed to be converted.
angle_types_member_map: optional, dict, default=None
The member types (atomtype string) for each atom associated with the angle_types the structure
Returns
-------
pmd_top_angletypes : dict
A dictionary linking a pmd.AngleType object to its
corresponding GMSO.AngleType object.
"""
pmd_top_angletypes = dict()
angle_types_member_map = _assert_dict(
angle_types_member_map, "angle_types_member_map"
)
for angletype in structure.angle_types:
angle_params = {
"k": (2 * angletype.k * u.Unit("kcal / (rad**2 * mol)")),
"theta_eq": (angletype.theteq * u.degree),
}
# Do we need to worry about Urey Bradley terms
# For Urey Bradley:
# k in (kcal/(angstrom**2 * mol))
# r_eq in angstrom
member_types = angle_types_member_map.get(id(angletype))
top_angletype = gmso.AngleType(
parameters=angle_params, member_types=member_types
)
pmd_top_angletypes[angletype] = top_angletype
return pmd_top_angletypes
def _dihedral_types_from_pmd(structure, dihedral_types_member_map=None):
"""Convert ParmEd dihedral types to GMSO DihedralType.
This function take in a Parmed Structure, iterate through its
dihedral_types and rb_torsion_types, create a corresponding
GMSO.DihedralType, and finally return a dictionary containing all
pairs of pmd.Dihedraltype (or pmd.RBTorsionType) and GMSO.DihedralType
Parameters
----------
structure: pmd.Structure
Parmed Structure that needed to be converted.
dihedral_types_member_map: optional, dict, default=None
The member types (atomtype string) for each atom associated with the dihedral_types the structure
Returns
-------
pmd_top_dihedraltypes : dict
A dictionary linking a pmd.DihedralType or pmd.RBTorsionType
object to its corresponding GMSO.DihedralType object.
"""
pmd_top_dihedraltypes = dict()
dihedral_types_member_map = _assert_dict(
dihedral_types_member_map, "dihedral_types_member_map"
)
for dihedraltype in structure.dihedral_types:
dihedral_params = {
"k": (dihedraltype.phi_k * u.Unit("kcal / mol")),
"phi_eq": (dihedraltype.phase * u.degree),
"n": dihedraltype.per * u.dimensionless,
}
member_types = dihedral_types_member_map.get(id(dihedraltype))
top_dihedraltype = gmso.DihedralType(
parameters=dihedral_params, member_types=member_types
)
pmd_top_dihedraltypes[dihedraltype] = top_dihedraltype
for dihedraltype in structure.rb_torsion_types:
dihedral_params = {
"c0": (dihedraltype.c0 * u.Unit("kcal/mol")),
"c1": (dihedraltype.c1 * u.Unit("kcal/mol")),
"c2": (dihedraltype.c2 * u.Unit("kcal/mol")),
"c3": (dihedraltype.c3 * u.Unit("kcal/mol")),
"c4": (dihedraltype.c4 * u.Unit("kcal/mol")),
"c5": (dihedraltype.c5 * u.Unit("kcal/mol")),
}
member_types = dihedral_types_member_map.get(id(dihedraltype))
top_dihedraltype = gmso.DihedralType(
parameters=dihedral_params,
expression="c0 * cos(phi)**0 + c1 * cos(phi)**1 + "
+ "c2 * cos(phi)**2 + c3 * cos(phi)**3 + c4 * cos(phi)**4 + "
+ "c5 * cos(phi)**5",
independent_variables="phi",
member_types=member_types,
)
pmd_top_dihedraltypes[dihedraltype] = top_dihedraltype
return pmd_top_dihedraltypes
def to_parmed(top, refer_type=True):
"""Convert a gmso.topology.Topology to a parmed.Structure.
At this point we only assume a three level structure for topology
Topology - Subtopology - Sites, which transform to three level of
Parmed Structure - Residue - Atoms.
If we decide to support multiple level Subtopology in the future,
this method will need some re-work. Tentative plan is to have the
Parmed Residue to be equivalent to the Subtopology right above Site.
Parameters
----------
top : topology.Topology
topology.Topology instance that need to be converted
refer_type : bool, optional, default=True
Whether or not to transfer AtomType, BondType, AngleTye,
and DihedralType information
Returns
-------
structure : parmed.Structure
"""
# Sanity check
msg = "Provided argument is not a topology.Topology."
assert isinstance(top, gmso.Topology)
# Set up Parmed structure and define general properties
structure = pmd.Structure()
structure.title = top.name
structure.box = np.concatenate(
(
top.box.lengths.to("angstrom").value,
top.box.angles.to("degree").value,
)
)
# Maps
subtop_map = dict() # Map site to subtop
atom_map = dict() # Map site to atom
bond_map = dict() # Map top's bond to structure's bond
angle_map = dict() # Map top's angle to strucutre's angle
dihedral_map = dict() # Map top's dihedral to structure's dihedral
# Set up unparametrized system
# Build subtop_map (site -> top)
default_residue = pmd.Residue("RES")
for subtop in top.subtops:
for site in subtop.sites:
subtop_map[site] = subtop
# Build up atom
for site in top.sites:
if site in subtop_map:
residue = subtop_map[site].name
residue_name = residue[: residue.find("[")]
residue_idx = int(
residue[residue.find("[") + 1 : residue.find("]")]
)
# since subtop contains information needed to build residue
else:
residue = default_residue
# Check element
if site.element:
atomic_number = site.element.atomic_number
charge = site.element.charge
else:
atomic_number = 0
charge = 0
pmd_atom = pmd.Atom(
atomic_number=atomic_number,
name=site.name,
mass=site.mass,
charge=site.charge,
)
pmd_atom.xx, pmd_atom.xy, pmd_atom.xz = site.position.to(
"angstrom"
).value
# Add atom to structure
structure.add_atom(pmd_atom, resname=residue_name, resnum=residue_idx)
atom_map[site] = pmd_atom
# "Claim" all of the item it contains and subsequently index all of its item
structure.residues.claim()
# Create and add bonds to Parmed structure
for bond in top.bonds:
site1, site2 = bond.connection_members
pmd_bond = pmd.Bond(atom_map[site1], atom_map[site2])
structure.bonds.append(pmd_bond)
bond_map[bond] = pmd_bond
# Create and add angles to Parmed structure
for angle in top.angles:
site1, site2, site3 = angle.connection_members
pmd_angle = pmd.Angle(atom_map[site1], atom_map[site2], atom_map[site3])
structure.angles.append(pmd_angle)
angle_map[angle] = pmd_angle
# Create and add dihedrals to Parmed structure
for dihedral in top.dihedrals:
site1, site2, site3, site4 = dihedral.connection_members
pmd_dihedral = pmd.Dihedral(
atom_map[site1], atom_map[site2], atom_map[site3], atom_map[site4]
)
if (
dihedral.connection_type
and dihedral.connection_type.expression
== parse_expr(
"c0 * cos(phi)**0 + "
+ "c1 * cos(phi)**1 + "
+ "c2 * cos(phi)**2 + "
+ "c3 * cos(phi)**3 + "
+ "c4 * cos(phi)**4 + "
+ "c5 * cos(phi)**5"
)
):
structure.rb_torsions.append(pmd_dihedral)
else:
structure.dihedrals.append(pmd_dihedral)
dihedral_map[dihedral] = pmd_dihedral
# Set up structure for Connection Type conversion
if refer_type:
# Need to add a warning if Topology does not have types information
if top.atom_types:
_atom_types_from_gmso(top, structure, atom_map)
if top.bond_types:
_bond_types_from_gmso(top, structure, bond_map)
if top.angle_types:
_angle_types_from_gmso(top, structure, angle_map)
if top.dihedral_types:
_dihedral_types_from_gmso(top, structure, dihedral_map)
return structure
def _atom_types_from_gmso(top, structure, atom_map):
"""Convert gmso.Topology AtomType to parmed.Structure AtomType.
This function will first check the AtomType expression of Topology and make sure it match with the one default in Parmed.
After that, it would start atomtyping and parametrizing this part of the structure.
Parameters
----------
top : topology.Topology
The topology that need to be converted
structure: parmed.Structure
The destination parmed Structure
"""
# Maps
atype_map = dict()
for atom_type in top.atom_types:
msg = "Atom type {} expression does not match Parmed AtomType default expression".format(
atom_type.name
)
assert atom_type.expression == parse_expr(
"4*epsilon*(-sigma**6/r**6 + sigma**12/r**12)"
), msg
# Extract Topology atom type information
atype_name = atom_type.name
# Convert charge to elementary_charge
atype_charge = float(atom_type.charge.to("Coulomb").value) / (
1.6 * 10 ** (-19)
)
atype_sigma = float(atom_type.parameters["sigma"].to("angstrom").value)
atype_epsilon = float(
atom_type.parameters["epsilon"].to("kcal/mol").value
)
atype_element = element_by_atom_type(atom_type)
atype_rmin = atype_sigma * 2 ** (1 / 6) / 2 # to rmin/2
# Create unique Parmed AtomType object
atype = pmd.AtomType(
atype_name,
None,
atype_element.mass,
atype_element.atomic_number,
atype_charge,
)
atype.set_lj_params(atype_epsilon, atype_rmin)
# Type map to match AtomType to its name
atype_map[atype_name] = atype
for site in top.sites:
# Assign atom_type to atom
pmd_atom = atom_map[site]
pmd_atom.type = site.atom_type.name
pmd_atom.atom_type = atype_map[site.atom_type.name]
def _bond_types_from_gmso(top, structure, bond_map):
"""Convert gmso.Topology BondType to parmed.Structure BondType.
This function will first check the BondType expression of Topology and make sure it match with the one default in Parmed.
After that, it would start atomtyping and parametrizing this part of the structure.
Parameters
----------
top : topology.Topology
The topology that need to be converted
structure: parmed.Structure
The destination parmed Structure
"""
btype_map = dict()
for bond_type in top.bond_types:
msg = "Bond type {} expression does not match Parmed BondType default expression".format(
bond_type.name
)
assert bond_type.expression == parse_expr("0.5 * k * (r-r_eq)**2"), msg
# Extract Topology bond_type information
btype_k = 0.5 * float(
bond_type.parameters["k"].to("kcal / (angstrom**2 * mol)").value
)
btype_r_eq = float(bond_type.parameters["r_eq"].to("angstrom").value)
# Create unique Parmed BondType object
btype = pmd.BondType(btype_k, btype_r_eq)
# Type map to match Topology BondType with Parmed BondType
btype_map[bond_type] = btype
# Add BondType to structure.bond_types
structure.bond_types.append(btype)
for bond in top.bonds:
# Assign bond_type to bond
pmd_bond = bond_map[bond]
pmd_bond.type = btype_map[bond.connection_type]
structure.bond_types.claim()
def _angle_types_from_gmso(top, structure, angle_map):
"""Convert gmso.Topology AngleType to parmed.Structure AngleType.
This function will first check the AngleType expression of Topology and make sure it match with the one default in Parmed.
After that, it would start atomtyping and parametrizing the structure.
Parameters
----------
top : topology.Topology
The topology that need to be converted
structure: parmed.Structure
The destination parmed Structure
"""
agltype_map = dict()
for angle_type in top.angle_types:
msg = "Angle type {} expression does not match Parmed AngleType default expression".format(
angle_type.name
)
assert angle_type.expression == parse_expr(
"0.5 * k * (theta-theta_eq)**2"
), msg
# Extract Topology angle_type information
agltype_k = 0.5 * float(
angle_type.parameters["k"].to("kcal / (rad**2 * mol)").value
)
agltype_theta_eq = float(
angle_type.parameters["theta_eq"].to("degree").value
)
# Create unique Parmed AngleType object
agltype = pmd.AngleType(agltype_k, agltype_theta_eq)
# Type map to match Topology AngleType with Parmed AngleType
agltype_map[angle_type] = agltype
# Add AngleType to structure.angle_types
structure.angle_types.append(agltype)
for angle in top.angles:
# Assign angle_type to angle
pmd_angle = angle_map[angle]
pmd_angle.type = agltype_map[angle.connection_type]
structure.angle_types.claim()
def _dihedral_types_from_gmso(top, structure, dihedral_map):
"""Convert gmso.Topology DihedralType to parmed.Structure DihedralType.
This function will first check the DihedralType expression of Topology and
make sure it match with the one default in Parmed.
After that, it would start atomtyping and parametrizing the structure.
Parameters
----------
top : topology.Topology
The topology that need to be converted
structure: parmed.Structure
The destination parmed Structure
"""
dtype_map = dict()
for dihedral_type in top.dihedral_types:
msg = "Dihedral type {} expression does not match Parmed DihedralType default expressions (Periodics, RBTorsions)".format(
dihedral_type.name
)
if dihedral_type.expression == parse_expr(
"k * (1 + cos(n * phi - phi_eq))**2"
):
dtype_k = float(dihedral_type.parameters["k"].to("kcal/mol").value)
dtype_phi_eq = float(
dihedral_type.parameters["phi_eq"].to("degrees").value
)
dtype_n = float(dihedral_type.parameters["n"].value)
# Create unique Parmed DihedralType object
dtype = pmd.DihedralType(dtype_k, dtype_n, dtype_phi_eq)
# Add DihedralType to structure.dihedral_types
structure.dihedral_types.append(dtype)
elif dihedral_type.expression == parse_expr(
"c0 * cos(phi)**0 + "
+ "c1 * cos(phi)**1 + "
+ "c2 * cos(phi)**2 + "
+ "c3 * cos(phi)**3 + "
+ "c4 * cos(phi)**4 + "
+ "c5 * cos(phi)**5"
):
dtype_c0 = float(
dihedral_type.parameters["c0"].to("kcal/mol").value
)
dtype_c1 = float(
dihedral_type.parameters["c1"].to("kcal/mol").value
)
dtype_c2 = float(
dihedral_type.parameters["c2"].to("kcal/mol").value
)
dtype_c3 = float(
dihedral_type.parameters["c3"].to("kcal/mol").value
)
dtype_c4 = float(
dihedral_type.parameters["c4"].to("kcal/mol").value
)
dtype_c5 = float(
dihedral_type.parameters["c5"].to("kcal/mol").value
)
# Create unique DihedralType object
dtype = pmd.RBTorsionType(
dtype_c0, dtype_c1, dtype_c2, dtype_c3, dtype_c4, dtype_c5
)
# Add RBTorsionType to structure.rb_torsion_types
structure.rb_torsion_types.append(dtype)
else:
raise GMSOException("msg")
dtype_map[dihedral_type] = dtype
for dihedral in top.dihedrals:
pmd_dihedral = dihedral_map[dihedral]
pmd_dihedral.type = dtype_map[dihedral.connection_type]
structure.dihedral_types.claim()
structure.rb_torsions.claim()
def _get_types_map(structure, attr):
"""Build `member_types` map for atoms, bonds, angles and dihedrals."""
assert attr in {"atoms", "bonds", "angles", "dihedrals", "rb_torsions"}
type_map = {}
for member in getattr(structure, attr):
conn_type_id, member_types = _get_member_types_map_for(member)
if conn_type_id not in type_map and all(member_types):
type_map[conn_type_id] = member_types
return type_map
def _get_member_types_map_for(member):
if isinstance(member, pmd.Atom):
return id(member.atom_type), member.type
if isinstance(member, pmd.Bond):
return id(member.type), (member.atom1.type, member.atom2.type)
if isinstance(member, pmd.Angle):
return id(member.type), (
member.atom1.type,
member.atom2.type,
member.atom3.type,
)
if isinstance(member, pmd.Dihedral):
return id(member.type), (
member.atom1.type,
member.atom2.type,
member.atom3.type,
member.atom4.type,
)
def _assert_dict(input_dict, param):
"""Provide default value for a dictionary and do a type check for a parameter."""
input_dict = {} if input_dict is None else input_dict
if not isinstance(input_dict, dict):
raise TypeError(
f"Expected `{param}` to be a dictionary. "
f"Got {type(input_dict)} instead."
)
return input_dict