class_docstr: A case-insensitive map of string keys to values.
  
  This is used by Python data source options to ensure consistent case insensitivity.
code: def __getitem__(self, key: str) -> Any:
      return super().__getitem__(key.lower())
  
imports: from abc import ABC, abstractmethod
  from collections import UserDict
  from typing import Any, Dict, Iterator, List, Sequence, Tuple, Type, Union, TYPE_CHECKING
  from pyspark.sql import Row
  from pyspark.sql.types import StructType
  from pyspark.errors import PySparkNotImplementedError
label_desc: Use image node_id 3 for calling the CaseInsensitiveDict obj's underlying member method code with example usage: obj.__getitem__(key) and returns: super