code: function(level) {    
          if (utils.isString(level) && levels.hasOwnProperty(level)) {
              process.env.LOG_LEVEL = levels[level];
          } 
          else if (!isNaN(parseInt(level, 10)) &&
                     utils.keyOf(parseInt(level, 10), levels)) {
              process.env.LOG_LEVEL = level;
          } 
          else {
              process.env.LOG_LEVEL = levels["ERROR"];                
          }
      }
docs: Normalize the value of the environment variable $LOG_LEVEL to an integer (look up named levels like "ERROR" in levels above), and default to "ERROR" if there is no value or an invalid value set.