function assertDatabaseIsEmpty (database, onProtocolError = () => {}, observer) {
  if (database) {
    const error = newError(
      'Driver is connected to the database that does not support multiple databases. ' +
        'Please upgrade to neo4j 4.0.0 or later in order to use this functionality'
    )

    // unsupported API was used, consider this a fatal error for the current connection
    onProtocolError(error.message)
    observer.onError(error)
    throw error
  }
}
Asserts that the passed-in database name is empty.
@param {string} database
@param {fuction(err: String)} onProtocolError Called when it doesn't have database set