Read/write. The URL of the hyperlink. URL can be on http, https,
        mailto, or file scheme; others may work. Returns |None| if no
        hyperlink is defined, including when another action such as
        `RUN_MACRO` is defined on the object. Assigning |None| removes any
        action defined on the object, whether it is a hyperlink action or
        not.

def address(self):
        """
        Read/write. The URL of the hyperlink. URL can be on http, https,
        mailto, or file scheme; others may work. Returns |None| if no
        hyperlink is defined, including when another action such as
        `RUN_MACRO` is defined on the object. Assigning |None| removes any
        action defined on the object, whether it is a hyperlink action or
        not.
        """
        hlink = self._hlink

        # there's no URL if there's no click action
        if hlink is None:
            return None

        # a click action without a relationship has no URL
        rId = hlink.rId
        if not rId:
            return None

        return self.part.target_ref(rId)