code: def add_param(param):
      # type: (Param) -> Callable
      
      def inner(o):
          try:
              getattr(o, 'parameters').add(param)
          except AttributeError:
              setattr(o, 'parameters', {param})
          return o
      return inner
docs: Add parameter, you should probably use on of :meth:`path_param`, :meth:`query_param`,
      :meth:`body_param`, or :meth:`header_param`.