Tap element identified by ``locator``.

        Args:
        - ``x_offset`` - (optional) x coordinate to tap, relative to the top left corner of the element.
        - ``y_offset`` - (optional) y coordinate. If y is used, x must also be set, and vice versa
        - ``count`` - can be used for multiple times of tap on that element

def tap(self, locator, x_offset=None, y_offset=None, count=1):
        """ Tap element identified by ``locator``.

        Args:
        - ``x_offset`` - (optional) x coordinate to tap, relative to the top left corner of the element.
        - ``y_offset`` - (optional) y coordinate. If y is used, x must also be set, and vice versa
        - ``count`` - can be used for multiple times of tap on that element
        """
        driver = self._current_application()
        el = self._element_find(locator, True, True)
        action = TouchAction(driver)
        action.tap(el,x_offset,y_offset, count).perform()