code: def relu(x):
      return x * (x > 0)
  
imports: import unittest
  import numpy
  import chainer
  from chainer.backends import cuda
  from chainer import gradient_check
  from chainer import links
  from chainer import testing
  from chainer import initializers
  from chainer.testing import attr
  from chainer.testing import condition
label_desc: Use image node_id 1 for calling a global function with example usage: relu(x) and returns: unknown