docstr: For backward compatibility, return the last metric as the full dict.
code: def get_last_metric(self):
      """For backward compatibility, return the last metric as the full dict."""
      return self._last_metric
  
file_path: nni/test/ut/sdk/helper/trial_command_channel.py
imports: from __future__ import annotations
  import copy
  from typing_extensions import Literal
  from nni.runtime.trial_command_channel import TrialCommandChannel
  from nni.typehint import TrialMetric, ParameterRecord
label_desc: Use image node_id 3 for calling the TestHelperTrialCommandChannel obj's underlying member method code with example usage: obj.get_last_metric() and returns: self