function normalizeSeverityToString(severity) {
	if ([2, "2", "error"].includes(severity)) {
		return "error";
	}
	if ([1, "1", "warn"].includes(severity)) {
		return "warn";
	}
	if ([0, "0", "off"].includes(severity)) {
		return "off";
	}
	throw new Error(`Invalid severity value: ${severity}`);
}
Convert severity value of different types to a string.
@param {string|number} severity severity value
@throws error if severity is invalid
@returns {string} severity string