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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 key_exists(self, section, key):
 """ Checks if given key exists. :param section: Current section to check key in. :type section: unicode :param key: Current key to check. :type key: unicode :return: Key existence. :rtype: bool """


        LOGGER.debug("> Checking '{0}' key existence in '{1}' section.".format(key, section))

        self.__settings.beginGroup(section)
        exists = self.__settings.contains(key)
        self.__settings.endGroup()
        return exists