code: def set_device_scale(self, x_scale, y_scale):
          
          cairo.cairo_surface_set_device_scale(self._pointer, x_scale, y_scale)
          self._check_status()
docs: Sets a scale that is multiplied to the device coordinates determined
          by the CTM when drawing to surface.
  
          One common use for this is to render to very high resolution display
          devices at a scale factor, so that code that assumes 1 pixel will be a
          certain size will still work.  Setting a transformation via
          cairo_translate() isn't sufficient to do this, since functions like
          cairo_device_to_user() will expose the hidden scale.
  
          Note that the scale affects drawing to the surface as well as using the
          surface in a source pattern.
  
          :param x_scale: the scale in the X direction, in device units.
          :param y_scale: the scale in the Y direction, in device units.
  
          *New in cairo 1.14.*
  
          *New in cairocffi 0.9.*