docs: function logLevelClass(level) {
          if (level) {
              var first = level[0];
              if (first === 'w' || first === "W") {
                  return "warning";
              }
              else if (first === 'e' || first === "E") {
                  return "error";
              }
              else if (first === 'i' || first === "I") {
                  return "info";
              }
              else if (first === 'd' || first === "D") {
                  // we have no debug css style
                  return "";
              }
          }
          return "";
      }