code: def test_builder_to_backend_stress_cast(
      self, compute_unit, backend, src_dst
  ):
      src_dtype, dst_dtype = src_dst
      x = np.array([[1, 2, 3], [4, 5, 6]], dtype=np.float32)
      numpy_pred = x.astype(dtype=np.float16)
  
      input_placeholder_dict = {"x": mb.placeholder(shape=x.shape)}
      input_value_dict = {"x": x}
  
      def build(x):
          x = mb.cast(x=x, dtype=src_dtype)
          x = mb.square(x=x)
          x = mb.cast(x=x, dtype=dst_dtype)
          x = mb.sqrt(x=x)
          x = mb.cast(x=x, dtype="fp32")
          return x
  
      expected_output_type = x.shape + (types.fp32,)
      run_compare_builder(
          build,
          input_placeholder_dict,
          input_value_dict,
          expected_output_type,
          numpy_pred,
          compute_unit=compute_unit,
          backend=backend,
      )
  
imports: import itertools
  import numpy
  import pytest
  import scipy
  from coremltools.converters.mil.mil import Builder
  from coremltools.converters.mil.mil import Function, get_new_symbol, types
  from coremltools.converters.mil.mil.ops.tests.iOS14 import backends
  from coremltools.converters.mil.mil.ops.tests.testing_utils import run_compare_builder
  from coremltools.converters.mil.mil.types.symbolic import is_compatible_symbolic_vector
  from coremltools.converters.mil.testing_reqs import compute_units
  from coremltools.converters.mil.testing_utils import ssa_fn
label_desc: Use image node_id 30 for calling the TestElementwiseUnary obj's underlying member method code with example usage: obj.test_builder_to_backend_stress_cast(compute_unit, backend, src_dst) and returns: x