code: def testCompileExternalPipelineOutputChannel(self):
      a = DummyNode("A")
      p1 = pipeline.Pipeline(
          pipeline_name="p1",
          components=[a],
          outputs={"x": a.output("x")},
      )
      p2_inputs = pipeline.PipelineInputs({"x": p1.outputs["x"]})
      p2 = pipeline.Pipeline(pipeline_name="p2", inputs=p2_inputs)
  
      ctx = compiler_context.PipelineContext(p2)
      result = pipeline_pb2.NodeInputs()
      node_inputs_compiler.compile_node_inputs(ctx, p2, result)
  
      self.assertLen(result.inputs, 1)
      self.assertLen(result.inputs["x"].channels, 1)
      self.assertProtoEquals(
          result.inputs["x"].channels[0],
          self._get_channel_pb(
              pipeline_name="p1", node_id="A", output_key="x"
          ),
      )
  
imports: from typing import List, Type
  from absl.testing import parameterized
  import tensorflow
  from tfx import types
  from tfx.dsl.compiler import compiler_context
  from tfx.dsl.compiler import node_inputs_compiler
  from tfx.dsl.components.base import base_component
  from tfx.dsl.components.base import base_node
  from tfx.dsl.components.base import executor_spec
  from tfx.dsl.control_flow import for_each
  from tfx.dsl.experimental.conditionals import conditional
  from tfx.dsl.experimental.node_execution_options import utils
  from tfx.dsl.input_resolution import resolver_function
  from tfx.dsl.input_resolution import resolver_op
  from tfx.dsl.placeholder import placeholder
  from tfx.orchestration import pipeline
  from tfx.proto.orchestration import pipeline_pb2
  from tfx.types import channel
  from tfx.types import channel_utils
  from tfx.types import component_spec
  from tfx.types import standard_artifacts
  from google.protobuf import text_format
label_desc: Use image node_id 6 for calling the NodeInputsCompilerTest obj's underlying member method code with example usage: obj.testCompileExternalPipelineOutputChannel() without return types