@abc.abstractmethod<EOL><INDENT>def get_agency(self, agency_id):<DEDENT>
return<EOL>
Gets the ``Agency`` specified by its ``Id``.

        In plenary mode, the exact ``Id`` is found or a ``NotFound``
        results. Otherwise, the returned ``Agency`` may have a different
        ``Id`` than requested, such as the case where a duplicate ``Id``
        was assigned to an ``Agency`` and retained for compatibility.

        :param agency_id: ``Id`` of the ``Agency``
        :type agency_id: ``osid.id.Id``
        :return: the agency
        :rtype: ``osid.authentication.Agency``
        :raise: ``NotFound`` -- ``agency_id`` not found
        :raise: ``NullArgument`` -- ``agency_id`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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