code: def ref_margin_loss(self, y, r, margin):
      n = len(y)
      dy = np.zeros(n)
      loss = 0
      if np.sum(np.abs(r)) < 1e-6:
          return loss, dy
  
      for i in range(n):
          for j in range(i + 1, n):
              weight = 1.0 / n
              diff = 1 if r[i] - r[j] > 0 else -1
              if (margin > (y[i] - y[j]) * diff) and (r[i] != r[j]):
                  loss += weight * (margin - (y[i] - y[j]) * diff)
                  dy[i] += -diff * weight
                  dy[j] += diff * weight
      return loss, dy
  
file_path: pytorch/caffe2/python/operator_test/margin_loss_l2r_operator_test.py
imports: import caffe2.python.hypothesis_test_util
  import hypothesis.strategies
  import numpy
  from caffe2.python import core, workspace
  from hypothesis import given
label_desc: Use image node_id 1 for calling the TestMarginLossL2rOps obj's underlying member method code with example usage: obj.ref_margin_loss(y, r, margin) and returns: loss,  dy, loss,  dy