OEReceptorSetInnerContourLevel
OEReceptorSetInnerContourLevel(rec: Union[OEGraphMol,OEMol,OEQMol],
level: float) -> bool
Sets the inner contour level on the receptor.
Returns true if successful.
It is only valid to call this function if receptor is a valid receptor
(i.e., OEIsReceptor returns true).