@abc.abstractmethod<EOL><INDENT>def get_packages_by_depots(self, depot_ids):<DEDENT>
return<EOL>
Gets the list of ``Packages`` corresponding to a list of ``Depots``.

        :param depot_ids: list of depot ``Ids``
        :type depot_ids: ``osid.id.IdList``
        :return: list of packages
        :rtype: ``osid.installation.PackageList``
        :raise: ``NullArgument`` -- ``depot_ids`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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