private com.google.protobuf.SingleFieldBuilder<
          main.Messages.StepValidateResponse, main.Messages.StepValidateResponse.Builder, main.Messages.StepValidateResponseOrBuilder> 
          getStepValidateResponseFieldBuilder() {
        if (stepValidateResponseBuilder_ == null) {
          stepValidateResponseBuilder_ = new com.google.protobuf.SingleFieldBuilder<
              main.Messages.StepValidateResponse, main.Messages.StepValidateResponse.Builder, main.Messages.StepValidateResponseOrBuilder>(
                  stepValidateResponse_,
                  getParentForChildren(),
                  isClean());
          stepValidateResponse_ = null;
        }
        return stepValidateResponseBuilder_;
      }