@abc.abstractmethod<EOL><INDENT>def search_among_repositories(self, repository_ids):<DEDENT>
pass<EOL>
Execute this search among the given list of repositories.

        :param repository_ids: list of repositories
        :type repository_ids: ``osid.id.IdList``
        :raise: ``NullArgument`` -- ``repository_ids`` is ``null``

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