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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 open(self, file, mode='r', perm=0o0644):
 """ Opens a file on the node :param file: file path to open :param mode: open mode :param perm: file permission in octet form mode: 'r' read only 'w' write only (truncate) '+' read/write 'x' create if not exist 'a' append :return: a file descriptor """

        args = {
            'file': file,
            'mode': mode,
            'perm': perm,
        }

        return self._client.json('filesystem.open', args)