new

# File actionpack/lib/action_dispatch/http/mime_type.rb, line 257
    def initialize(string, symbol = nil, synonyms = [])
      unless MIME_REGEXP.match?(string)
        raise InvalidMimeType, "#{string.inspect} is not a valid MIME type"
      end
      @symbol, @synonyms = symbol, synonyms
      @string = string
      @hash = [@string, @synonyms, @symbol].hash
    end