def click(self, focus=None, sleep_interval=None):
        """
        Perform the click action on the UI element(s) represented by the UI proxy. If this UI proxy represents a set of
        UI elements, the first one in the set is clicked and the anchor point of the UI element is used as the default
        one. It is also possible to click another point offset by providing ``focus`` argument.

        See ``CoordinateSystem`` for more details.

        Args:
            focus (2-:obj:`tuple`/2-:obj:`list`/:obj:`str`): an offset point (x, y) from the top left corner of the UI
             element(s), values must be in range of 0~1. This argument can be also specified by 'anchor' or 'center'.
             'Center' means to click the center of bounding box of UI element. 
            sleep_interval: number of seconds to wait after this action. Default is None which is the default sleep
             interval. This value can be configured by Poco initialization. See configuration at poco
             :py:class:`initialization <poco.pocofw.Poco>` for more details.

        Raises:
            PocoNoSuchNodeException: raised when the UI element does not exist
        """

        focus = focus or self._focus or 'anchor'
        pos_in_percentage = self.get_position(focus)
        self.poco.pre_action('click', self, pos_in_percentage)
        ret = self.poco.click(pos_in_percentage)
        if sleep_interval:
            time.sleep(sleep_interval)
        else:
            self.poco.wait_stable()
        self.poco.post_action('click', self, pos_in_percentage)
        return ret
Perform the click action on the UI element(s) represented by the UI proxy. If this UI proxy represents a set of
        UI elements, the first one in the set is clicked and the anchor point of the UI element is used as the default
        one. It is also possible to click another point offset by providing ``focus`` argument.

        See ``CoordinateSystem`` for more details.

        Args:
            focus (2-:obj:`tuple`/2-:obj:`list`/:obj:`str`): an offset point (x, y) from the top left corner of the UI
             element(s), values must be in range of 0~1. This argument can be also specified by 'anchor' or 'center'.
             'Center' means to click the center of bounding box of UI element. 
            sleep_interval: number of seconds to wait after this action. Default is None which is the default sleep
             interval. This value can be configured by Poco initialization. See configuration at poco
             :py:class:`initialization <poco.pocofw.Poco>` for more details.

        Raises:
            PocoNoSuchNodeException: raised when the UI element does not exist