def queueStringCommand(self, command, public=1):
        """
        Queues a string to be issued as an FTP command

        @param command: string of an FTP command to queue
        @param public: a flag intended for internal use by FTPClient.  Don't
            change it unless you know what you're doing.

        @return: a L{Deferred} that will be called when the response to the
            command has been received.
        """
        ftpCommand = FTPCommand(command, public)
        self.queueCommand(ftpCommand)
        return ftpCommand.deferred

        Queues a string to be issued as an FTP command

        @param command: string of an FTP command to queue
        @param public: a flag intended for internal use by FTPClient.  Don't
            change it unless you know what you're doing.

        @return: a L{Deferred} that will be called when the response to the
            command has been received.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/protocols/ftp.py