code: def get_child_book_ids(self, book_id):
          
          # Implemented from template for
          # osid.resource.BinHierarchySession.get_child_bin_ids
          if self._catalog_session is not None:
              return self._catalog_session.get_child_catalog_ids(catalog_id=book_id)
          return self._hierarchy_session.get_children(id_=book_id)
docs: Gets the child ``Ids`` of the given book.
  
          arg:    book_id (osid.id.Id): the ``Id`` to query
          return: (osid.id.IdList) - the children of the book
          raise:  NotFound - ``book_id`` is not found
          raise:  NullArgument - ``book_id`` is ``null``
          raise:  OperationFailed - unable to complete request
          raise:  PermissionDenied - authorization failure
          *compliance: mandatory -- This method must be implemented.*