code: def _calc_score(self, batch, ys):
      return sum(x[batch, y] for x, y in zip(self.xs, ys)) + sum(
          self.cost[y1, y2] for y1, y2 in zip(ys[:-1], ys[1:])
      )
  
imports: import itertools
  import unittest
  import numpy
  import chainer
  from chainer.backends import cuda
  from chainer import functions
  from chainer import gradient_check
  from chainer import testing
  from chainer.testing import attr
label_desc: Use image node_id 2 for calling the TestCRF1d obj's underlying member method code with example usage: obj._calc_score(batch, ys) and returns: unknown