private org.nd4j.shade.protobuf.RepeatedFieldBuilderV3<
          org.nd4j.ir.MapperNamespace.MappingRule, org.nd4j.ir.MapperNamespace.MappingRule.Builder, org.nd4j.ir.MapperNamespace.MappingRuleOrBuilder> 
          getRuleFieldBuilder() {
        if (ruleBuilder_ == null) {
          ruleBuilder_ = new org.nd4j.shade.protobuf.RepeatedFieldBuilderV3<