code: def add_n_trend(trend_input, average_time, initial_trend, subs, subscript_dict):
      
  
      stateful = {
          'py_name': utils.make_python_identifier('_trend_%s_%s_%s' % (trend_input,
                                                                      average_time,
                                                                      initial_trend))[0],
          'real_name': 'trend of %s' % trend_input,
          'doc': 'Trend average time: %s \n Trend initial value %s' % (
              average_time, initial_trend),
          'py_expr': 'functions.Trend(lambda: %s, lambda: %s, lambda: %s)' % (
              trend_input, average_time, initial_trend),
          'unit': 'None',
          'lims': 'None',
          'eqn': 'None',
          'subs': '',
          'kind': 'stateful',
          'arguments': ''
      }
  
      return "%s()" % stateful['py_name'], [stateful]
docs: Trend.
  
          Parameters
          ----------
          trend_input: <string>
  
          average_time: <string>
  
  
          trend_initial: <string>
  
          subs: list of strings
              List of strings of subscript indices that correspond to the
              list of expressions, and collectively define the shape of the output
              See `builder.add_flaux` for more info
  
          Returns
          -------
          reference: basestring
              reference to the trend object `__call__` method, which will return the output
              of the trend process
  
          new_structure: list
              list of element construction dictionaries for the builder to assemble