private com.google.protobuf.SingleFieldBuilder<
          main.Messages.StepValidateRequest, main.Messages.StepValidateRequest.Builder, main.Messages.StepValidateRequestOrBuilder> 
          getStepValidateRequestFieldBuilder() {
        if (stepValidateRequestBuilder_ == null) {
          stepValidateRequestBuilder_ = new com.google.protobuf.SingleFieldBuilder<
              main.Messages.StepValidateRequest, main.Messages.StepValidateRequest.Builder, main.Messages.StepValidateRequestOrBuilder>(
                  stepValidateRequest_,
                  getParentForChildren(),
                  isClean());
          stepValidateRequest_ = null;
        }
        return stepValidateRequestBuilder_;
      }