code: def test_sign(self, X, exponent, gc, dc):
      def signf(X):
          return [np.sign(X)]
  
      op = core.CreateOperator("Sign", ["X"], ["Y"])
  
      self.assertReferenceChecks(
          gc, op, [X], signf, ensure_outputs_are_inferred=True
      )
      self.assertDeviceChecks(dc, op, [X], [0])
  
file_path: pytorch/caffe2/python/operator_test/math_ops_test.py
imports: from caffe2.python import core
  from hypothesis import given, settings
  from hypothesis import strategies
  import caffe2.python.hypothesis_test_util
  import caffe2.python.serialized_test.serialized_test_util
  import numpy
  import unittest
label_desc: Use image node_id 2 for calling the TestMathOps obj's underlying member method code with example usage: obj.test_sign(X, exponent, gc, dc) and returns: list