Creates the batch file to run the experiment.

def _batch(self):
        '''
        Creates the batch file to run the experiment.
        '''
        self.batch = '%s/%s.treeliker' % (self.tmpdir, self.basename)

        commands = []
        if not self.test_dataset:
            commands.append('set(output_type, single)')
            commands.append("set(examples, '%s.txt')" % self.basename)
        else:
            commands.append('set(output_type, train_test)')
            commands.append("set(train_set, '%s.txt')" % self.basename)
            commands.append("set(test_set, '%s_test.txt')" % self.basename)
        commands.append('set(template, %s)' % self.template)

        if not self.test_dataset:
            commands.append('set(output, %s.arff)' % self.basename)
        else:
            commands.append('set(output, conversion)')

        # Optional settings
        for key, val in self.settings.items():
            if val not in [None, '']:
                commands.append('set(%s, %s)' % (key, str(val)))

        commands.append('work(yes)')

        with open(self.batch, 'w') as f:
            f.write('\n'.join(commands))