code: def configure_count(self, ns, definition):
          
          @self.add_route(ns.collection_path, Operation.Count, ns)
          @qs(definition.request_schema)
          @wraps(definition.func)
          def count(**path_data):
              request_data = load_query_string_data(definition.request_schema)
              response_data = dict()
              count = definition.func(**merge_data(path_data, request_data))
              headers = encode_count_header(count)
              definition.header_func(headers, response_data)
              response_format = self.negotiate_response_content(definition.response_formats)
              return dump_response_data(
                  None,
                  None,
                  headers=headers,
                  response_format=response_format,
              )
  
          count.__doc__ = "Count the size of the collection of all {}".format(pluralize(ns.subject_name))
docs: Register a count endpoint.
  
          The definition's func should be a count function, which must:
          - accept kwargs for the query string
          - return a count is the total number of items available
  
          The definition's request_schema will be used to process query string arguments.
  
          :param ns: the namespace
          :param definition: the endpoint definition