code: def testAsOutputChannel(self):
      node1 = mock.MagicMock()
      node1.id = "n1"
      ch1 = channel.Channel(type=_MyType)
      ch1.additional_properties["string_value"] = "foo"
      ch1.additional_custom_properties["another_string_value"] = "bar"
      ch2 = ch1.as_output_channel(node1, "x")
  
      with self.subTest("Expected Attributes"):
          self.assertEqual(ch2.type, _MyType)
          self.assertEqual(
              ch2.additional_properties, {"string_value": "foo"}
          )
          self.assertEqual(
              ch2.additional_custom_properties,
              {"another_string_value": "bar"},
          )
          self.assertEqual(ch2.producer_component_id, "n1")
          self.assertEqual(ch2.output_key, "x")
  
      with self.subTest("AdditionalProperty Mutation"):
          ch1.additional_properties["string_value"] = "foo2"
          ch1.additional_custom_properties[
              "another_string_value"
          ] = "bar2"
          self.assertEqual(
              ch2.additional_properties, {"string_value": "foo2"}
          )
          self.assertEqual(
              ch2.additional_custom_properties,
              {"another_string_value": "bar2"},
          )
  
imports: from unittest import mock
  import tensorflow
  from tfx.dsl.input_resolution import resolver_op
  from tfx.dsl.placeholder import placeholder
  from tfx.types import artifact
  from tfx.types import channel
  from tfx.types import resolved_channel
  from google.protobuf import struct_pb2
  from ml_metadata.proto import metadata_store_pb2
label_desc: Use image node_id 10 for calling the ChannelTest obj's underlying member method code with example usage: obj.testAsOutputChannel() without return types