    # File lib/rack/request.rb, line 376
          def parse_http_accept_header(header)
            header.to_s.split(/\s*,\s*/).map do |part|
              attribute, parameters = part.split(/\s*;\s*/, 2)
              quality = 1.0
              if parameters and /\Aq=([\d.]+)/ =~ parameters
                quality = $1.to_f
              end
              [attribute, quality]
            end
          end