# File lib/www/mechanize/chain/custom_headers.rb, line 7
        def handle(ctx, params)
          request = params[:request]
          params[:headers].each do |k,v|
            case k
            when :etag then request["ETag"] = v
            when :if_modified_since then request["If-Modified-Since"] = v
            else
              raise ArgumentError.new("unknown header symbol #{k}") if k.is_a? Symbol
              request[k] = v
            end
          end
          super
        end