code: def __getitem__(self, key):
      if key == "gt_fields":
          return [
              field
              for field in self._dict["gt_fields"]
              if self.get(field, None) is not None
          ]
      return super().__getitem__(key)
  
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 SampleDict obj's underlying member method code with example usage: obj.__getitem__(key) and returns: super, unknown