code: def _add_to_docstring(string):
      '''Private wrapper function. Appends ``string`` to the
      docstring of the wrapped function.
  
      '''
      def wrapper(method):
          if method.__doc__ is not None:
              method.__doc__ += string
          else:
              method.__doc__ = string
          return method
      return wrappef _add_to_docstring(string):
      '''Private wrapper function. Appends ``string`` to the
      docstring of the wrapped function.
  
      '''
      def wrapper(method):
          if method.__doc__ is not None:
              method.__doc__ += string
          else:
              method.__doc__ = string
          return method
      return wrapper
docs: Private wrapper function. Appends ``string`` to the
      docstring of the wrapped function.