changed name of attribute of HBondGroup.___atom_str_list to .__atom_str_tuple Added asserts to its corresponding set method to assert it is a tuple of strs.
changed name of attribute of HBondGroup.___atom_str_list to .__atom_str_tuple
Added asserts to its corresponding set method to assert it is a tuple of strs.

jruhym/intrapeptideContacts,jruhym/intrapeptideContacts