code: private String getSMRID(PhysicalEntity pe)
  	{
  		if (pe instanceof SmallMolecule)
  		{
  			EntityReference er = ((SmallMolecule) pe).getEntityReference();
  			if (er != null) return er.getUri();
  		}
  		return null;
  	}
docs: Gets the ID of the reference of the given entity if it is a small molecule.