code: def test_builder_acos_eval(self):
      val = np.array([[-1, -0.5, 0], [0.4, 0.5, 0.8]], dtype=np.float32)
      v = mb.acos(x=val)
      expected_outputs = np.array(
          [
              [3.14159265, 2.0943951, 1.57079633],
              [1.15927948, 1.04719755, 0.64350111],
          ],
          dtype=np.float32,
      )
      assert is_close(expected_outputs, v.val)
  
imports: import scipy
  from coremltools.converters.mil import testing_reqs
  from coremltools.converters.mil.testing_reqs import *
  from .testing_utils import run_compare_builder
label_desc: Use image node_id 3 for calling the TestElementwiseUnary obj's underlying member method code with example usage: obj.test_builder_acos_eval() without return types