code: def test_observe_zero_dimensions(self):
      observer = action_metrics.ContinuousActionObserver()
      observer.observe_first(env=_FAKE_ENV, timestep=_TIMESTEP)
      observer.observe(
          env=_FAKE_ENV, timestep=_TIMESTEP, action=np.array(1)
      )
      self.assertEqual(
          {
              "action[]_max": 1,
              "action[]_min": 1,
              "action[]_mean": 1,
              "action[]_p50": 1,
          },
          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 5 for calling the ActionMetricsTest obj's underlying member method code with example usage: obj.test_observe_zero_dimensions() without return types