code: def test_grayscale_input(
      self,
      rank4_input_model,
      rank3_input_model,
      rank4_grayscale_input_model,
  ):
      with pytest.raises(ValueError, match="must have rank 4"):
          mlmodel = ct.convert(
              rank3_input_model,
              inputs=[
                  ct.ImageType(color_layout=ct.colorlayout.GRAYSCALE)
              ],
              minimum_deployment_target=ct.target.macOS13,
          )
  
      # invalid shape
      with pytest.raises(ValueError):
          mlmodel = ct.convert(
              rank4_input_model,
              inputs=[
                  ct.ImageType(color_layout=ct.colorlayout.GRAYSCALE)
              ],
              minimum_deployment_target=ct.target.macOS13,
          )
  
      mlmodel = ct.convert(
          rank4_grayscale_input_model,
          inputs=[ct.ImageType(color_layout=ct.colorlayout.GRAYSCALE)],
          outputs=[ct.TensorType(dtype=np.float32)],
          minimum_deployment_target=ct.target.macOS13,
      )
      assert_ops_in_mil_program(
          mlmodel, expected_op_list=["cast", "transpose", "add", "cast"]
      )
      assert_spec_input_image_type(
          mlmodel._spec,
          expected_feature_type=ft.ImageFeatureType.GRAYSCALE,
      )
      assert_prog_input_type(
          mlmodel._mil_program, expected_dtype_str="fp32"
      )
      assert_prog_output_type(
          mlmodel._mil_program, expected_dtype_str="fp32"
      )
      verify_prediction(mlmodel)
  
      with pytest.raises(
          TypeError,
          match="float16 dtype for inputs is only supported for deployment target >= iOS16/macOS13",
      ):
          mlmodel = ct.convert(
              rank4_grayscale_input_model,
              inputs=[
                  ct.ImageType(
                      color_layout=ct.colorlayout.GRAYSCALE_FLOAT16
                  )
              ],
              minimum_deployment_target=ct.target.macOS12,
          )
  
      # test that grayscale_16 raises error when used with neural network
      with pytest.raises(
          TypeError,
          match="float16 dtype for inputs is only supported for deployment target >= iOS16/macOS13",
      ):
          mlmodel = ct.convert(
              rank4_grayscale_input_model,
              inputs=[
                  ct.ImageType(
                      color_layout=ct.colorlayout.GRAYSCALE_FLOAT16
                  )
              ],
          )
  
      mlmodel = ct.convert(
          rank4_grayscale_input_model,
          inputs=[
              ct.ImageType(
                  color_layout=ct.colorlayout.GRAYSCALE_FLOAT16
              )
          ],
          outputs=[ct.TensorType(dtype=np.float16)],
          minimum_deployment_target=ct.target.macOS13,
      )
      assert_ops_in_mil_program(
          mlmodel, expected_op_list=["transpose", "add"]
      )
      assert_spec_input_image_type(
          mlmodel._spec,
          expected_feature_type=ft.ImageFeatureType.GRAYSCALE_FLOAT16,
      )
      assert_prog_input_type(
          mlmodel._mil_program, expected_dtype_str="fp16"
      )
      assert_output_dtype(mlmodel, expected_type_str="fp16")
      verify_prediction(mlmodel)
  
imports: import itertools
  import os
  import tempfile
  import numpy
  import pytest
  import coremltools
  from coremltools._deps import _HAS_TF_1, _HAS_TF_2, MSG_TF1_NOT_FOUND
  from coremltools.converters.mil.testing_reqs import backends, compute_units
  from coremltools.converters.mil.testing_utils import assert_cast_ops_count, assert_input_dtype, assert_ops_in_mil_program, assert_output_dtype, assert_prog_input_type, assert_prog_output_type, assert_spec_input_image_type, assert_spec_output_image_type, get_op_types_in_program, verify_prediction
  from coremltools.proto import FeatureTypes_pb2
  from coremltools.test.api.test_api_examples import TestInputs
label_desc: Use image node_id 14 for calling the TestInputOutputConversionAPI obj's underlying member method code with example usage: obj.test_grayscale_input(rank4_input_model, rank3_input_model, rank4_grayscale_input_model) without return types