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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 _validate_args(self, args):
        ''' validate the user arguments '''
        assert(args.bucket)

        if args.subscribers:
            for _subscriber in args.subscribers:
                assert(isinstance(_subscriber, AsperaBaseSubscriber))

        if (args.transfer_config):
            assert(isinstance(args.transfer_config, AsperaConfig))

            # number of sessions requested cant be greater than max ascps
            if args.transfer_config.multi_session > self._config.ascp_max_concurrent:
                raise ValueError("Max sessions is %d" % self._config.ascp_max_concurrent)

        for _pair in args.file_pair_list:
            if not _pair.key or not _pair.fileobj:
                raise ValueError("Invalid file pair")