def system_to_molecule(self):
return Molecule(self.system, self.system_id, <NUM_LIT:0>)<EOL>
Return :class:`MolecularSystem` as a :class:`Molecule` directly.

Only to be used conditionally, when the :class:`MolecularSystem` is a
discrete molecule and no input pre-processing is required.

Returns
-------
:class:`pywindow.molecular.Molecule`
    :class:`Molecule`