docs: function setLevel(newLogLevel) {
           if (isNaN(newLogLevel) || newLogLevel < 0 || newLogLevel > LEVELS.silly) {
               throw Error(`setLevel(): invalid level: ${newLogLevel}`);
           }
  
           logLevel = newLogLevel;
           Object.keys(LEVELS).forEach((levelName, levelIndex) => {
               if (levelIndex <= logLevel) {
                   logger[levelName] = function logit() {
                       const msgArgs = [levelName].concat([].slice.call(arguments));
                       writeLog.apply(writeLog, msgArgs);
                   };
               } else {
                   logger[levelName] = () => {};
               }
  
           });
       }