def __init__(self, name=None):
"""Initialize the MoleculeType container.
Args:
name (str): the name of the moleculetype to add
"""
if not name:
name = 'MOL'
self.name = name
self.molecules = OrderedSet()
self.bond_forces = set()
self.pair_forces = set()
self.angle_forces = set()
self.dihedral_forces = set()
self.virtual_forces = set()
self.torsiontorsion_forces = set()
self.constraints = set()
self.exclusions = set()
self.rigidwaters = set()
self.nrexcl = None
