@abc.abstractmethod<EOL><INDENT>def get_objective_bank_ids_by_proficiency(self, proficiency_id):<DEDENT>
return<EOL>
Gets the ``ObjectiveBank``  ``Ids`` mapped to a ``Proficiency``.

        :param proficiency_id: ``Id`` of a ``Proficiency``
        :type proficiency_id: ``osid.id.Id``
        :return: list of objective banks
        :rtype: ``osid.id.IdList``
        :raise: ``NotFound`` -- ``proficiency_id`` is not found
        :raise: ``NullArgument`` -- ``proficiency_id`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

        *compliance: mandatory -- This method must be implemented.*