code: def test_get_downstream_artifacts_by_artifact_uri(self):
      # Test: get downstream artifacts by example_2, with max_num_hops = 0
      result_from_exp2 = (
          self.resolver.get_downstream_artifacts_by_artifact_uri(
              self.e2.uri, max_num_hops=0
          )
      )
      self.assertLen(result_from_exp2, 1)
      self.assertIn(self.e2.id, result_from_exp2)
      self.assertCountEqual(
          [result_from_exp2[self.e2.id][0].name], [self.e2.name]
      )
  
      # Test: get downstream artifacts by example_2, with max_num_hops = 2
      result_from_exp2 = (
          self.resolver.get_downstream_artifacts_by_artifact_uri(
              self.e2.uri, max_num_hops=2
          )
      )
      self.assertLen(result_from_exp2, 1)
      self.assertIn(self.e2.id, result_from_exp2)
      self.assertCountEqual(
          [artifact.name for artifact in result_from_exp2[self.e2.id]],
          [self.e2.name, self.m1.name, self.m2.name],
      )
  
      # Test: get downstream artifacts by example_2, with max_num_hops = 20
      result_from_exp2 = (
          self.resolver.get_downstream_artifacts_by_artifact_uri(
              self.e2.uri, max_num_hops=20
          )
      )
      self.assertLen(result_from_exp2, 1)
      self.assertIn(self.e2.id, result_from_exp2)
      self.assertCountEqual(
          [artifact.name for artifact in result_from_exp2[self.e2.id]],
          [self.e2.name, self.m1.name, self.m2.name, self.ev1.name],
      )
  
      # Test: get downstream artifacts by example_2, with max_num_hops
      # unspecified.
      result_from_exp2 = (
          self.resolver.get_downstream_artifacts_by_artifact_uri(
              self.e2.uri
          )
      )
      self.assertLen(result_from_exp2, 1)
      self.assertIn(self.e2.id, result_from_exp2)
      self.assertCountEqual(
          [artifact.name for artifact in result_from_exp2[self.e2.id]],
          [self.e2.name, self.m1.name, self.m2.name, self.ev1.name],
      )
  
      # Test: raise ValueError if `artifact_uri` is empty.
      with self.assertRaisesRegex(
          ValueError, "`artifact_uri` is empty."
      ):
          self.resolver.get_downstream_artifacts_by_artifact_uri("")
  
imports: from typing import Dict, List
  from absl.testing import absltest
  from ml_metadata import metadata_store
  from ml_metadata.proto import metadata_store_pb2
  from ml_metadata.tools.mlmd_resolver import metadata_resolver
  from ml_metadata.tools.mlmd_resolver import metadata_resolver_utils
label_desc: Use image node_id 3 for calling the MetadataResolverTest obj's underlying member method code with example usage: obj.test_get_downstream_artifacts_by_artifact_uri() without return types