public B sessionFactory(CassandraStorage.SessionFactory sessionFactory) {
    if (sessionFactory == null) throw new NullPointerException("sessionFactory == null");
    this.sessionFactory = sessionFactory;
    return (B) this;
  }
Override to control how sessions are created.
zipkin-storage/cassandra/src/main/java/zipkin2/storage/cassandra/CassandraStorageBuilder.java