code: def get_relationship_lookup_session(self, proxy):
          
          if not self.supports_relationship_lookup():
              raise errors.Unimplemented()
          # pylint: disable=no-member
          return sessions.RelationshipLookupSession(proxy=proxy, runtime=self._runtime)
docs: Gets the ``OsidSession`` associated with the relationship lookup service.
  
          arg:    proxy (osid.proxy.Proxy): a proxy
          return: (osid.relationship.RelationshipLookupSession) - a
                  ``RelationshipLookupSession``
          raise:  NullArgument - ``proxy`` is ``null``
          raise:  OperationFailed - unable to complete request
          raise:  Unimplemented - ``supports_relationship_lookup()`` is
                  ``false``
          *compliance: optional -- This method must be implemented if
          ``supports_relationship_lookup()`` is ``true``.*