code: def test_bad_monitor(self, _):
      state = {torchbearer.METRICS: {"acc_loss": 0.1}}
  
      file_path = "test_file_{acc_loss:.2f}"
      check = Best(file_path, monitor="test_fail")
      check.on_start(state)
  
      with warnings.catch_warnings(record=True) as w:
          check.on_checkpoint(state)
          self.assertTrue(len(w) == 1)
  
imports: from unittest import TestCase
  from mock import patch, Mock
  import torchbearer
  from torchbearer import Trial
  from torchbearer.callbacks.checkpointers import _Checkpointer, ModelCheckpoint, MostRecent, Interval, Best
  import warnings
label_desc: Use image node_id 9 for calling the TestBest obj's underlying member method code with example usage: obj.test_bad_monitor(_) without return types