/**
 * Get Access token from Google API
 * @param {string} clientId OAuth Client ID
 * @param {string} clientSecret OAuth Client Secret
 * @param {string} refreshToken OAuth Refresh token
 * @returns {Promise<string>} Access token
 * @example const accessToken = await getAccessToken('123456-...', 'ABCD-...', '1//ABCD123...')
 */
export declare const getAccessToken: (clientId: string, clientSecret: string, refreshToken: string) => Promise<string>;