code: def forward_xp(self, inputs, xp):
      raise NotImplementedError(
          "Op test implementation must override `forward_xp`."
      )
  
imports: import numpy
  import chainer
  from chainer import functions
  import chainerx
  from chainerx_tests import dtype_utils
  from chainerx_tests import op_utils
label_desc: Use image node_id 5 for calling the LossBase obj's underlying member method code with example usage: obj.forward_xp(inputs, xp) without return types