code: def map(self, map_fn, name="Map"):
          
          op = Operator(
              _generate_uuid(),
              OpType.Map,
              name,
              map_fn,
              num_instances=self.env.config.parallelism)
          return self.__register(op)
docs: Applies a map operator to the stream.
  
          Attributes:
               map_fn (function): The user-defined logic of the map.