    # File lib/action_controller/mime_type.rb, line 65
          def register(string, symbol, mime_type_synonyms = [], extension_synonyms = [], skip_lookup = false)
            Mime.instance_eval { const_set symbol.to_s.upcase, Type.new(string, symbol, mime_type_synonyms) }

            SET << Mime.const_get(symbol.to_s.upcase)

            ([string] + mime_type_synonyms).each { |string| LOOKUP[string] = SET.last } unless skip_lookup
            ([symbol.to_s] + extension_synonyms).each { |ext| EXTENSION_LOOKUP[ext] = SET.last }
          end