class_docstr: KLDivLoss
code: def _kl_div(self, x, label, mask=None):
      y = (label * (paddle.log(label + 1e-10) - x)).sum(axis=1)
      if mask is not None:
          y = y.masked_select(mask).mean()
      else:
          y = y.mean()
      return y
  
imports: import paddle
  import paddle.nn
  import paddle.nn.functional
  from paddle.nn import L1Loss
  from paddle.nn import MSELoss
  from paddle.nn import SmoothL1Loss
label_desc: Use image node_id 3 for calling the DKDLoss obj's underlying member method code with example usage: obj._kl_div(x, label, mask) and returns: y