code: def testInvalidDictionaryOutputError(self):
      b = UnitB()
      dag = {
          b: dag_pipeline.DagInput(b.input_type),
          dag_pipeline.DagOutput(): b,
      }
      with self.assertRaises(dag_pipeline.InvalidDictionaryOutputError):
          dag_pipeline.DAGPipeline(dag)
  
      a = UnitA()
      dag = {
          a: dag_pipeline.DagInput(b.input_type),
          dag_pipeline.DagOutput("output"): a,
      }
      with self.assertRaises(dag_pipeline.InvalidDictionaryOutputError):
          dag_pipeline.DAGPipeline(dag)
  
      a2 = UnitA()
      dag = {
          a: dag_pipeline.DagInput(a.input_type),
          a2: dag_pipeline.DagInput(a2.input_type),
          dag_pipeline.DagOutput("output"): {
              "t1": a["t1"],
              "t2": a2["t2"],
          },
      }
      with self.assertRaises(dag_pipeline.InvalidDictionaryOutputError):
          dag_pipeline.DAGPipeline(dag)
  
imports: import collections
  from absl.testing import absltest
  from magenta.pipelines import dag_pipeline
  from magenta.pipelines import pipeline
  from magenta.pipelines import statistics
label_desc: Use image node_id 17 for calling the DAGPipelineTest obj's underlying member method code with example usage: obj.testInvalidDictionaryOutputError() without return types