code: def testProtoFutureValueOperator(self):
      output_channel = Channel(type=standard_artifacts.Integer)
      placeholder = output_channel.future()[0].value
      channel_to_key = {output_channel: "_component.num"}
      self.assertProtoEquals(
          channel_utils.encode_placeholder_with_channels(
              placeholder, lambda k: channel_to_key[k]
          ),
          load_testdata(
              "proto_placeholder_future_value_operator.pbtxt"
          ),
      )
  
imports: import os
  from typing import Type, TypeVar
  from absl.testing import parameterized
  import tensorflow
  from tfx.dsl.placeholder import placeholder
  from tfx.proto.orchestration import placeholder_pb2
  from tfx.types import channel_utils
  from tfx.types import standard_artifacts
  from tfx.types.artifact import Artifact
  from tfx.types.artifact import Property
  from tfx.types.artifact import PropertyType
  from tfx.types.channel import Channel
  from google.protobuf import message
  from google.protobuf import text_format
label_desc: Use image node_id 1 for calling the ChannelWrappedPlaceholderTest obj's underlying member method code with example usage: obj.testProtoFutureValueOperator() without return types