code: def user_to_device(self, x, y):
          
          xy = ffi.new('double[2]', [x, y])
          cairo.cairo_user_to_device(self._pointer, xy + 0, xy + 1)
          self._check_status()
          return tuple(xy)
docs: Transform a coordinate from user space to device space
          by multiplying the given point
          by the current transformation matrix (CTM).
  
          :param x: X position.
          :param y: Y position.
          :type x: float
          :type y: float
          :returns: A ``(device_x, device_y)`` tuple of floats.