code: def forward_expected(self, inputs):
      x, W = inputs
      y_expect = x.copy()
      masked = numpy.ma.masked_greater_equal(y_expect, 0, copy=False)
      shape = (1,) + W.shape + (1,) * (x.ndim - W.ndim - 1)
      masked *= W.reshape(shape)
      return (y_expect,)
  
file_path: chainer/tests/chainer_tests/functions_tests/activation_tests/test_prelu.py
imports: import numpy
  import chainer
  from chainer import functions
  from chainer import testing
label_desc: Use image node_id 3 for calling the TestPReLU obj's underlying member method code with example usage: obj.forward_expected(inputs) and returns: y_expect