/**
 * Retrieves the value of a nested property from a JSON object based on a dot-separated key path.
 * Converts the retrieved value into the specified return type (number, string, or boolean).
 *
 * @param {Record<string, unknown>} obj - The source object containing nested key-value pairs.
 * @param {string} key - Dot-separated path to the desired property (e.g., 'temperature.tC').
 * @param {'number' | 'string' | 'boolean'} returnType - The type to convert the retrieved value into.
 * @returns {number | string | boolean | null} - The converted value or null if the property doesn't exist.
 *
 * Example usage:
 * const value = getNestedValue(data, 'temperature.tC', 'number'); // Returns 47.1
 */
export declare function getNestedValue(obj: Record<string, unknown>, key: string, returnType: 'number' | 'string' | 'boolean'): number | string | boolean | null;
/**
 * Checks if a nested key exists in the given object.
 *
 * @param obj - The object to search within.
 * @param key - The nested key path, specified as a dot-separated string (e.g., "level1.level2").
 * @returns {boolean} - True if the key exists, otherwise false.
 */
export declare function hasNestedKey(obj: Record<string, unknown>, key: string): boolean;