# File lib/thin/logging.rb, line 81
      def trace_logger=(custom_tracer)
        [ :level   ,
          :level=  ,
          :debug   ,
          :info    ,
          :warn    ,
          :error   ,
          :fatal   ,
          :unknown ,
        ].each do |method|
          if not custom_tracer.respond_to?(method)
            raise ArgumentError, "trace logger must respond to #{method}"
          end
        end

        @trace_logger = custom_tracer
      end