old_contents: from chainer import function
  from chainer import function_set
  from chainer.functions import basic_math
  from chainer import optimizer
  from chainer import variable
  
  Variable = variable.Variable
  Function = function.Function
  FunctionSet = function_set.FunctionSet
  Optimizer = optimizer.Optimizer
  
  basic_math.install_variable_arithmetics()
  
new_contents: import pkg_resources
  
  from chainer import function
  from chainer import function_set
  from chainer.functions import basic_math
  from chainer import optimizer
  from chainer import variable
  
  
  __version__ = pkg_resources.get_distribution('chainer').version
  
  Variable = variable.Variable
  Function = function.Function
  FunctionSet = function_set.FunctionSet
  Optimizer = optimizer.Optimizer
  
  basic_math.install_variable_arithmetics()
  
subject: Add version number to chainer module