@utilities.remove_null_proxy_kwarg<EOL><INDENT>def get_bank_hierarchy_session(self):<DEDENT>
if not self.supports_bank_hierarchy():<EOL><INDENT>raise errors.Unimplemented()<EOL><DEDENT>return sessions.BankHierarchySession(runtime=self._runtime)<EOL>
Gets the session traversing bank hierarchies.

        return: (osid.assessment.BankHierarchySession) - a
                ``BankHierarchySession``
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented - ``supports_bank_hierarchy() is false``
        *compliance: optional -- This method must be implemented if
        ``supports_bank_hierarchy()`` is true.*