code: def prune(self):
      super().prune()
      for field in self._dict["map_fields"]:
          if field not in self:
              self._dict["map_fields"].remove(field)
  
imports: from itertools import cycle
  from collections import OrderedDict
  from collections.abc import MutableMapping
  import paddle
label_desc: Use image node_id 2 for calling the NetOutDict obj's underlying member method code with example usage: obj.prune() without return types