code: def test_external_source_fail_missing_output():
      class ExternalSourcePipeline(Pipeline):
          def __init__(
              self, batch_size, external_s_size, num_threads, device_id
          ):
              super().__init__(batch_size, num_threads, device_id)
              self.input = ops.ExternalSource()
              self.input_2 = ops.ExternalSource()
              self.batch_size_ = batch_size
              self.external_s_size_ = external_s_size
  
          def define_graph(self):
              self.batch = self.input()
              self.batch_2 = self.input_2()
              return [self.batch]
  
          def iter_setup(self):
              batch = datapy.zeros([self.external_s_size_, 4, 5])
              self.feed_input(self.batch, batch)
              self.feed_input(self.batch_2, batch)
  
      batch_size = 3
      pipe = ExternalSourcePipeline(batch_size, batch_size, 3, 0)
      pipe.build()
      assert_raises(
          RuntimeError,
          pipe.run,
          regex=r"Could not find an input operator with name .*",
      )
  
imports: import functools
  import numpy
  import nvidia.dali.fn
  import nvidia.dali.ops
  from nvidia.dali import Pipeline
  from nose_utils import assert_raises
  from test_utils import check_output
label_desc: Use image node_id 28 for calling a global function with example usage: test_external_source_fail_missing_output() and returns: list