code: def test_builder_to_backend_smoke(self, use_cpu_only, backend):
      elem_shape = (2,)
      input_placeholders = {
          "a": mb.placeholder(shape=elem_shape),
          "b": mb.placeholder(shape=elem_shape),
      }
  
      def build(a, b):
          ls = mb.make_list(init_length=2, elem_shape=elem_shape)
          # list is initially all 0
          init_t = mb.list_read(ls=ls, index=0)
          ls = mb.list_write(ls=ls, index=0, value=a)
          # this write is out of bound
          ls = mb.list_write(ls=ls, index=4, value=b)
          ls = mb.list_scatter(
              ls=ls,
              indices=[2, 1],
              value=np.array([[-1, -2], [-4, -5]], dtype=np.float32),
          )
          return (
              init_t,
              mb.list_read(ls=ls, index=0),
              mb.list_gather(ls=ls, indices=[4, 2, 3]),
          )
  
      input_values = {
          "a": np.array([1, 3], dtype=np.float32),
          "b": np.array([2, 4], dtype=np.float32),
      }
  
      expected_output_types = [
          (2, types.fp32),
          (2, types.fp32),
          (3, 2, types.fp32),
      ]
  
      expected_outputs = [
          np.array([0, 0], dtype=np.float32),
          np.array([1, 3], dtype=np.float32),
          np.array([[2, 4], [-1, -2], [0, 0]], dtype=np.float32),
      ]
      run_compare_builder(
          build,
          input_placeholders,
          input_values,
          expected_output_types,
          expected_outputs,
          use_cpu_only=use_cpu_only,
          frontend_only=False,
          backend=backend,
      )
  
file_path: turicreate/src/external/coremltools_wrap/coremltools/coremltools/converters/mil/mil/ops/tests/test_control_flow.py
imports: from coremltools.converters.mil import testing_reqs
  from coremltools.converters.mil.testing_reqs import *
  from .testing_utils import run_compare_builder, UNK_SYM
label_desc: Use image node_id 1 for calling the TestList obj's underlying member method code with example usage: obj.test_builder_to_backend_smoke(use_cpu_only, backend) and returns: init_t,  mb,  mb