/**
 * Opens a new session, or resumes the previous session if this device had activity within
 * the `sessionTimeoutInSeconds` value.
 *
 * Call `openSession` at the end of your initialization code section, after any calls to `changeUser` or
 * `setIdentifierToken`. Calling `openSession` before either function may result in the creation of duplicate anonymous
 * users and multiple sessions.
 *
 * @returns Resolves to a boolean that indicates whether a new session was started. Resolves to undefined if the SDK has
 *   not been initialized.
 */
export declare function openSession(): Promise<boolean | undefined>;