code: def test_observe_nothing(self):
      observer = action_metrics.ContinuousActionObserver()
      self.assertEqual({}, observer.get_metrics())
  
file_path: acme/acme/utils/observers/action_metrics_test.py
imports: from acme import specs
  from acme.testing import fakes
  from acme.utils.observers import action_metrics
  import dm_env
  import numpy
  from absl.testing import absltest
label_desc: Use image node_id 1 for calling the ActionMetricsTest obj's underlying member method code with example usage: obj.test_observe_nothing() without return types