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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 retrieve(self, filename):
 """ Run the FTP RETR command, and download the file :param filename: Name of the file to download """

        logger.debug('Sending FTP retr command. Filename: {}'.format(filename))
        self.client.retrbinary('RETR {}'.format(filename), self._save_file)