@abc.abstractmethod<EOL><INDENT>def get_assignable_depot_ids(self, depot_id):<DEDENT>
return<EOL>
Gets a list of depot including and under the given depot node in which any package can be assigned.

        :param depot_id: the ``Id`` of the ``Depot``
        :type depot_id: ``osid.id.Id``
        :return: list of assignable depot ``Ids``
        :rtype: ``osid.id.IdList``
        :raise: ``NullArgument`` -- ``depot_id`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request

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