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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 __register_driver(self, channel, webdriver):
        "Register webdriver to a channel."

        # Add to list of webdrivers to cleanup.
        if not self.__registered_drivers.has_key(channel):
            self.__registered_drivers[channel] = []  # set to new empty array

        self.__registered_drivers[channel].append(webdriver)

        # Set singleton instance for the channel
        self.__webdriver[channel] = webdriver