OEReceptorGetBoundLigand
OEReceptorGetBoundLigand(rec: Union[OEGraphMol,OEMol,OEQMol]) -> OEGraphMol
Returns a copy of the receptor’s bound ligand.
If the receptor does not have a bound ligand then an empty molecule will be returned
It is only valid to call this function if receptor is a valid receptor
(i.e., OEIsReceptor returns true).