docs: def get_repositories_by_ids(self, repository_ids=None):
          """Gets a ``RepositoryList`` corresponding to the given ``IdList``.
  
          In plenary mode, the returned list contains all of the
          repositories specified in the ``Id`` list, in the order of the
          list, including duplicates, or an error results if an ``Id`` in
          the supplied list is not found or inaccessible. Otherwise,
          inaccessible ``Repositories`` may be omitted from the list and
          may present the elements in any order including returning a
          unique set.
  
          :param repository_ids: the list of ``Ids`` to retrieve
          :type repository_ids: ``osid.id.IdList``
          :return: the returned ``Repository list``
          :rtype: ``osid.repository.RepositoryList``
          :raise: ``NotFound`` -- an ``Id`` was not found
          :raise: ``NullArgument`` -- ``repository_ids`` is ``null``
          :raise: ``OperationFailed`` -- unable to complete request
          :raise: ``PermissionDenied`` -- authorization failure
  
          *compliance: mandatory -- This method must be implemented.*
  
          """
          if repository_ids is None:
              raise NullArgument()
          repositories = []
          for i in repository_ids:
              repository = None
              url_path = construct_url('objective_banks',
                                       bank_id=i)
              try:
                  repository = self._get_request(url_path)
              except (NotFound, OperationFailed):
                  if self._repository_view == PLENARY:
                      raise
                  else:
                      pass
              if repository:
                  if not (self._repository_view == COMPARATIVE and
                          repository in repositories):
                      repositories.append(repository)
          return objects.RepositoryList(repositories)