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import { Key, Values } from "../libs/types.ts";import { RULE, ValueSchemaError } from "../libs/ValueSchemaError.ts";export interface Rules<T> {    /** value if undefined (defaults: error) */    ifUndefined?: T | null | undefined;}/** * apply schema * @param values input/output values * @param rules rules * @param keyStack key stack for error handling * @returns escapes from applyTo chain or not */export function applyTo<T>(values: Values, rules: Rules<T>, keyStack: Key[]): values is Values<T> {    if (values.output !== undefined) {        return false;    }    if (!rules.hasOwnProperty("ifUndefined")) {        return ValueSchemaError.raise(RULE.UNDEFINED, values, keyStack);    }    values.output = rules.ifUndefined;    return true;}