# File lib/main/mode.rb, line 19
    def find_by_mode m, options = {}
      quiet = options['quiet'] || options[:quiet]
      each_pair do |mode, klass|
        return mode if mode == m
      end
      candidates = []
      each_pair do |mode, klass|
        candidates << mode if mode.index(m) == 0
      end
      case candidates.size
        when 0
          nil
        when 1
          candidates.first
        else
          raise Ambiguous, "ambiguous mode: #{ m } = (#{ candidates.sort.join ' or ' })?"
      end
    end