class_docstr: Parametric Rectified Linear Unit function.
code: def forward_cpu(self, inputs):
      x, W = inputs
      y = x.copy()
      masked = numpy.ma.masked_greater_equal(y, 0, copy=False)
      shape = _get_extended_shape(W, y)
      masked *= W.reshape(shape)
      self.retain_inputs((0, 1))
      return (y,)
  
imports: import numpy
  import chainer
  from chainer.backends import cuda
  from chainer import function_node
  from chainer.utils import type_check
label_desc: Use image node_id 2 for calling the PReLUFunction obj's underlying member method code with example usage: obj.forward_cpu(inputs) and returns: y