@Override
  public AsyncTableBuilder<C> setRequestAttribute(String key, byte[] value) {
    if (requestAttributes.isEmpty()) {
      requestAttributes = new HashMap<>();
    }
    requestAttributes.put(key, value);
    return this;
  }
Base class for all asynchronous table builders.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/AsyncTableBuilderBase.java