class_docstr: Heartbeat controls the userspace trial state updates.
  
  For unmanaged / detached trials, this class will report the state changes
  to the determined-master.
  
  For managed trials, it'll not do anything as the state is controlled by
  determined-master itself.
code: def close(
      self,
      exc_type: Optional[type],
      exc_val: Optional[BaseException],
      exc_tb: Optional[types.TracebackType],
  ) -> "_Heartbeat":
      return self
  
imports: import atexit
  import logging
  import sys
  import threading
  import time
  import types
  from typing import Any, Optional, Union
  from determined.common import api
  from determined.common.api import bindings
label_desc: Use image node_id 3 for calling the _Heartbeat obj's underlying member method code with example usage: obj.close(exc_type, exc_val, exc_tb) and returns: self