class_docstr: Class for managing value based locking.
code: def __init__(self):
      self._main_lock = threading.Lock()
      self._locks: MutableMapping[typing.Hashable, threading.Lock] = {}
      self._refcounts = collections.defaultdict(int)
  
imports: import collections
  import contextlib
  import copy
  import threading
  import typing
  from typing import Callable, Iterator, MutableMapping, Optional
  import cachetools
  from tfx.orchestration import metadata
  from google.protobuf.internal import containers
  from ml_metadata.proto import metadata_store_pb2
label_desc: Use image node_id 1 to create a new _LocksManager object  with example: obj = _LocksManager()