code: def open_database(parameters):
      
      spanner_client = spanner.Client()
      instance_id = parameters['cloudspanner.instance']
      instance = spanner_client.instance(instance_id)
      database_id = parameters['cloudspanner.database']
      pool = spanner.BurstyPool(int(parameters['num_worker']))
      database = instance.database(database_id, pool=pool)
  
      return database
docs: Opens a database specified by the parameters from parse_options().