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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 get_network_name(network_id):
 """ Return the keeper network name based on the current ethereum network id. Return `development` for every network id that is not mapped. :param network_id: Network id, int :return: Network name, str """

        if os.environ.get('KEEPER_NETWORK_NAME'):
            logging.debug('keeper network name overridden by an environment variable: {}'.format(
                os.environ.get('KEEPER_NETWORK_NAME')))
            return os.environ.get('KEEPER_NETWORK_NAME')

        return Keeper._network_name_map.get(network_id, Keeper.DEFAULT_NETWORK_NAME)