code: def is_available():
      return _error is None
  
file_path: chainer/chainer/testing/unary_math_function_test.py
imports: import unittest
  import warnings
  import numpy
  from chainer.backends import cuda
  from chainer import function
  from chainer import functions
  from chainer import variable
label_desc: Use image node_id 1 for calling a global function with example usage: is_available() and returns: unknown