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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 getdefault(self):
 """Return an available default downloader."""


        if not self.available:
            error('No supported downloaders available')
            print('\nPlease install one of the following:', file=sys.stderr)
            print(self.SUPPORTED, file=sys.stderr)
            sys.exit(1)

        default = Config.DOWNLOADER_DEFAULT

        if default in self.available:
            return default
        else:
            alternative = self.available[0]
            warning('Default downloader {!r} not available, using {!r} instead'
                    .format(Config.DOWNLOADER_DEFAULT, alternative))
            return alternative