code: def test_builder_to_backend_symbolic(self, use_cpu_only, backend):
      s0 = get_new_symbol()
  
      x_val = np.array(
          [
              [1, 2, 3, 4, 5, 0, 0, 0],
              [1, 2, 0, 0, 0, 0, 0, 0],
              [1, 2, 3, 4, 0, 0, 0, 0],
              [1, 2, 3, 4, 5, 6, 7, 8],
          ],
          dtype=np.float32,
      )
      input_placeholders = {"x": mb.placeholder(shape=(4, s0))}
      input_values = {"x": x_val}
  
      def build(x):
          return [
              mb.reverse_sequence(
                  x=x, lengths=[7, 2, 3, 5], seq_axis=1, batch_axis=0
              ),
          ]
  
      expected_output_types = [
          (4, s0, types.fp32),
      ]
      expected_outputs = [
          np.array(
              [
                  [0, 0, 5, 4, 3, 2, 1, 0],
                  [2, 1, 0, 0, 0, 0, 0, 0],
                  [3, 2, 1, 4, 0, 0, 0, 0],
                  [5, 4, 3, 2, 1, 6, 7, 8],
              ],
              dtype=np.float32,
          )
      ]
  
      run_compare_builder(
          build,
          input_placeholders,
          input_values,
          expected_output_types,
          expected_outputs,
          use_cpu_only=use_cpu_only,
          backend=backend,
      )
  
imports: from coremltools.converters.mil import testing_reqs
  from coremltools.converters.mil.mil import get_new_symbol, get_new_variadic_symbol
  from coremltools.converters.mil.testing_reqs import *
  from .testing_utils import UNK_SYM, UNK_VARIADIC, run_compare_builder
label_desc: Use image node_id 2 for calling the TestReverseSequence obj's underlying member method code with example usage: obj.test_builder_to_backend_symbolic(use_cpu_only, backend) and returns: list