code: def grab_to_file(filename, childprocess=None, backend=None):
      
      if childprocess is None:
          childprocess = childprocess_default_value()
      return _grab(to_file=True, childprocess=childprocess,
                   backend=backend, filename=filename)
docs: Copy the contents of the screen to a file. Internal function! Use
      PIL.Image.save() for saving image to file.
  
      :param filename: file for saving
      :param childprocess: see :py:func:`grab`
      :param backend: see :py:func:`grab`