Matcher engine: ruled, unruled, unparsed.

def matcher(self):
        """
        Matcher engine: ruled, unruled, unparsed.
        """
        if self.args.matcher is None:
            return 'ruled'
        elif self.args.matcher.startswith('-'):
            matcher = self.args.matcher.strip('-').replace('-', '_')
        else:
            matcher = self.args.matcher

        if matcher not in ['ruled', 'unruled', 'unparsed']:
            raise LogRaptorArgumentError('matcher', 'unknown matcher argument %r' % matcher)
        return matcher