code: def _validate_all_tags_are_used(metadata):
      
      tag_names = set([tag_name for tag_name, _ in metadata.tags])
      filter_arg_names = set()
      for location, _ in metadata.registered_locations:
          for filter_info in metadata.get_filter_infos(location):
              for filter_arg in filter_info.args:
                  if is_tag_argument(filter_arg):
                      filter_arg_names.add(get_directive_argument_name(filter_arg))
  
      unused_tags = tag_names - filter_arg_names
      if unused_tags:
          raise GraphQLCompilationError(u'This GraphQL query contains @tag directives whose values '
                                        u'are not used: {}. This is not allowed. Please either use '
                                        u'them in a filter or remove them entirely.'
                                        .format(unused_tags))
docs: Ensure all tags are used in some filter.