code: function(ruleConfig) {
  			var severity = Array.isArray(ruleConfig) ? ruleConfig[0] : ruleConfig;
  
  			if (typeof severity === "string") {
  				severity = severity.toLowerCase();
  			}
  			return VALID_SEVERITIES.indexOf(severity) !== -1;
  		}
docs: Checks whether a given config has valid severity or not.
  @param {number|string|Array} ruleConfig - The configuration for an individual rule.
  @returns {boolean} `true` if the configuration has valid severity.