code: def _thread_lock_storage(cls):
          
          if not hasattr(threadlocal, 'limpyd_locked_fields'):
              threadlocal.limpyd_locked_fields = {}
          if cls._name not in threadlocal.limpyd_locked_fields:
              threadlocal.limpyd_locked_fields[cls._name] = set()
          return threadlocal.limpyd_locked_fields[cls._name]
docs: We mark each locked field in a thread, to allow other operations in the
          same thread on the same field (for the same instance or others). This
          way, operations within the lock, in the same thread, can bypass it (the
          whole set of operations must be locked)