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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def install_addon(self, path, temporary=None):
 """ Installs Firefox addon. Returns identifier of installed addon. This identifier can later be used to uninstall addon. :param path: Absolute path to the addon that will be installed. :Usage: :: driver.install_addon('/path/to/firebug.xpi') """

        payload = {"path": path}
        if temporary is not None:
            payload["temporary"] = temporary
        return self.execute("INSTALL_ADDON", payload)["value"]