  * @property {number} time - timestamp of endpoint.
   * @property {string} type - A type defined in |ENDPOINT_TYPES|.
   * originates from.
   */

  /**
   * Returns an array of endpoints. An endpoint is either the start or end
   * timestamp of a TimedEvent.
   *
   * @param {Array.<!tr.model.TimedEvent>} events - Events to extract endpoints
   * from.
   * @param {string} startType - Endpoint type for a start time endpoint.
   * @param {string} endType - Endpoint type for an end time endpoint.
   * @ret