public void putObjectExtra(String key, Object value) {
    // concurrenthashmap will throw NPE when key or value is null
    if (key == null || value == null) {
      return;
    }
    if (mExtraData == null) {
      mExtraData = new ConcurrentHashMap<>();
    }
    mExtraData.put(key, value);
  }
Get the top level context chain, which can be the current context chain itself.
fbcore/src/main/java/com/facebook/common/callercontext/ContextChain.java