code: def __getitem__(self, item):
      return self.d[item]
  
imports: from __future__ import annotations
  import heapq
  import operator
  import pickle
  import random
  from collections.abc import Mapping
  import pytest
  from distributed.collections import LRU, HeapSet, sum_mappings
label_desc: Use image node_id 2 for calling the ReadOnlyMapping obj's underlying member method code with example usage: obj.__getitem__(item) and returns: self