code: def test_apply_diff_mapping():
      src = {"a": 1}
      dest = {"b": 2}
      apply_diff(src, dest)
      assert dest == src, "Adds and removes keys"
  
      src = {"a": 1}
      dest = {"a": MyInt(1)}
      apply_diff(src, dest)
      assert type(dest["a"]) is MyInt, "Does not replace equals"
  
      src = {"d": {"a": 1}}
      inner = {}
      dest = {"d": inner}
      apply_diff(src, dest)
      assert dest["d"] is inner, "Updates inner dicts"
  
file_path: dvc/tests/unit/utils/test_collections.py
imports: import json
  import pytest
  from dvc.utils.collections import apply_diff, merge_dicts, remove_missing_keys, to_omegaconf
  from dvc.utils.serialize import dumps_yaml
label_desc: Use image node_id 2 for calling a global function with example usage: test_apply_diff_mapping() without return types