class_docstr: Rename fields using a mapping, if source field present.
  
  Parameters
  ----------
  mapping
      Name mapping `input_name -> output_name`
code: def transform(self, data: DataEntry):
      for key, new_key in self.mapping.items():
          if key in data:
              # no implicit overriding
              assert new_key not in data
              data[new_key] = data[key]
              del data[key]
      return data
  
imports: from collections import Counter
  from typing import Any, Dict, List
  from gluonts.core.component import validated
  from gluonts.dataset.common import DataEntry
  from ._base import MapTransformation, SimpleTransformation
label_desc: Use image node_id 2 for calling the RenameFields obj's underlying member method code with example usage: obj.transform(data) and returns: data