code: def test_empty_block():
      """
      Test an empty program
      """
  
      @mb.program(input_specs=[mb.TensorSpec(shape=(2, 4))])
      def prog(x0):
          return x0
  
      block = prog.functions["main"]
      assert len(block.operations) == 0
      assert len(block.inputs) == 1
      assert len(block.outputs) == 1
      assert block.inputs["x0"] == block.outputs[0]
  
imports: import copy
  import numpy
  import pytest
  from coremltools.converters.mil.mil import Builder
  from coremltools.converters.mil.mil.passes.tests.test_passes import CONSTEXPR_FUNCS
  from coremltools.converters.mil.testing_utils import assert_same_output_names, assert_same_output_shapes, get_op_types_in_program
label_desc: Use image node_id 1 for calling a global function with example usage: test_empty_block() and returns: x0