code: function (levels, fn) {
      return function (label, val) {
          for (var i = 0; i < levels.length; i++) {
              if (levels[i] === exports.level) {
                  return fn(label, val);
              }
          }
      };
  }
docs: Executes a function only if the current log level is in the levels list
  
  @param {Array} levels
  @param {Function} fn