code: def declare_backward_dependency(self, out_grad, in_data, out_data):
          
          deps = []
          if self.need_top_grad_:
              deps.extend(out_grad)
          deps.extend(in_data)
          deps.extend(out_data)
          return deps
docs: Declare dependencies of this operator for backward pass.
  
          Parameters
          ----------
          out_grad : list of int
              ids of out_grad blobs.
          in_data : list of int
              ids of in_data blobs.
          out_data: list of int
              ids of out_data blobs.
  
          Returns
          -------
          deps : list of int
              ids of the needed blobs.