code: public ExecutionChain setErrorCallback(ErrorCallback callback) {
          if (state.get() == State.RUNNING) {
              throw new IllegalStateException(
                      "Invalid while ExecutionChain is running");
          }
          errorCallback = callback;
          return this;
      }
docs: Set a callback to handle any exceptions in the chain of execution.
  
  @param callback
  Instance of {@link ErrorCallback}.
  @return Reference to the {@code ExecutionChain}
  @throws IllegalStateException
  if the chain of execution has already been {@link #execute()
  started}.