docstr: Since a fp16 output bug in Core ML can only be reproduced by non-CPU backends,
  for this test, we hardcode the compute_unit.
docstr_tok: ["Since","a","fp16","output","bug","in","Core","ML","can","only","be","reproduced","by","non-CPU","backends",",","for","this","test",",","we","hardcode","the","compute_unit","."]
code: def test_cast_fp16_output_bug_smoke(self, compute_unit, backend):
      """
      Since a fp16 output bug in Core ML can only be reproduced by non-CPU backends,
      for this test, we hardcode the compute_unit.
      """
  
      def build(x):
          return mb.cast(x=x, dtype="fp16")
  
      x = np.array([[1, 2, 3], [4, 5, 6]], dtype=np.int32)
      expected_res = x.astype(dtype=np.float16)
  
      mlmodel = run_compare_builder(
          build,
          {"x": mb.placeholder(shape=x.shape, dtype=types.int32)},
          input_values={"x": x},
          expected_output_types=x.shape + (types.fp16,),
          expected_outputs=expected_res,
          compute_unit=compute_unit,
          backend=backend,
      )
  
      prog = mlmodel._mil_program
      assert get_op_types_in_program(prog) == ["cast"]
      cast_op = prog.find_ops(op_type="cast", exactly_one=True)[0]
      assert cast_op.dtype.val == "fp16"
  
file_path: coremltools/coremltools/converters/mil/mil/ops/tests/iOS17/test_elementwise_unary.py
imports: import itertools
  from unittest.mock import patch
  import numpy
  import pytest
  import coremltools
  from coremltools.converters.mil.mil import Builder
  from coremltools.converters.mil.mil import types
  from coremltools.converters.mil.mil.ops.tests.iOS14.test_elementwise_unary import TestElementwiseUnary
  from coremltools.converters.mil.mil.ops.tests.iOS17 import backends
  from coremltools.converters.mil.mil.ops.tests.testing_utils import run_compare_builder
  from coremltools.converters.mil.mil.passes.pass_pipeline import PassPipeline
  from coremltools.converters.mil.mil.types.type_mapping import numpy_type_to_builtin_type
  from coremltools.converters.mil.mil.var import Var
  from coremltools.converters.mil.testing_reqs import compute_units
  from coremltools.converters.mil.testing_utils import get_op_types_in_program
label_desc: Use image node_id 4 for calling the TestElementwiseUnary obj's underlying member method code with example usage: obj.test_cast_fp16_output_bug_smoke(compute_unit, backend) and returns: mb