Flick starting at on_element, and moving by the xoffset and yoffset
        with specified speed.

        :Args:
         - on_element: Flick will start at center of element.
         - xoffset: X offset to flick to.
         - yoffset: Y offset to flick to.
         - speed: Pixels per second to flick.

def flick_element(self, on_element, xoffset, yoffset, speed):
        """
        Flick starting at on_element, and moving by the xoffset and yoffset
        with specified speed.

        :Args:
         - on_element: Flick will start at center of element.
         - xoffset: X offset to flick to.
         - yoffset: Y offset to flick to.
         - speed: Pixels per second to flick.
        """
        self._actions.append(lambda: self._driver.execute(
            Command.FLICK, {
                'element': on_element.id,
                'xoffset': int(xoffset),
                'yoffset': int(yoffset),
                'speed': int(speed)}))
        return self