new_contents: import unittest
  import numpy as np
  from op_test import OpTest
  
  
  class TestReshapeOp(OpTest):
      def setUp(self):
          self.op_type = "rank_loss"
          num = 5
          # P = {0, 1.0} or {0, 0.5, 1.0}
          P = np.random.randint(0, 2, size=(num, num)).astype("float32")
          Oi = np.random.random((num, num)).astype("float32")
          Oj = np.random.random((num, num)).astype("float32")
          O = Oi - Oj
          Out = np.log(1.0 + np.exp(O)) - P * O
          self.inputs = {'P': P, 'Oi': Oi, 'Oj': Oj}
          self.outputs = {'Out': Out}
  
      def test_check_output(self):
          self.check_output()
  
      def test_check_grad(self):
          self.check_grad(["Oj"], "Out")
  
  
  if __name__ == '__main__':
      unittest.main()
  
subject: add unit test for rank_loss_op