    # File lib/merb-core/controller/mixins/responder.rb, line 364
        def content_type=(type)
          unless Merb.available_mime_types.has_key?(type)
            raise Merb::ControllerExceptions::NotAcceptable.new("Unknown content_type for response: #{type}")
          end

          @_content_type = type

          mime = Merb.available_mime_types[type]

          headers["Content-Type"] = mime[:content_type]

          # merge any format specific response headers
          mime[:response_headers].each { |k,v| headers[k] ||= v }

          # if given, use a block to finetune any runtime headers
          mime[:response_block].call(self) if mime[:response_block]

          @_content_type
        end