Long press on an element.

        :Args:
         - on_element: The element to long press.

def long_press(self, on_element):
        """
        Long press on an element.

        :Args:
         - on_element: The element to long press.
        """
        self._actions.append(lambda: self._driver.execute(
            Command.LONG_PRESS, {'element': on_element.id}))
        return self