docs: 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