class_docstr: Rename fields using a mapping, if source field present.
  
  Parameters
  ----------
  mapping
      Name mapping `input_name -> output_name`
code: def __init__(self, mapping: Dict[str, str]) -> None:
      self.mapping = mapping
      values_count = Counter(mapping.values())
      for new_key, count in values_count.items():
          assert (
              count == 1
          ), f"Mapped key {new_key} occurs multiple time"
  
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 1 to create a new RenameFields object from inherited base classes: SimpleTransformation with example: obj = RenameFields(mapping)