private com.google.protobuf.SingleFieldBuilder<
          org.bwapi.proxy.messages.GameMessages.UnitId, org.bwapi.proxy.messages.GameMessages.UnitId.Builder, org.bwapi.proxy.messages.GameMessages.UnitIdOrBuilder> 
          getCarrierFieldBuilder() {
        if (carrierBuilder_ == null) {
          carrierBuilder_ = new com.google.protobuf.SingleFieldBuilder<
              org.bwapi.proxy.messages.GameMessages.UnitId, org.bwapi.proxy.messages.GameMessages.UnitId.Builder, org.bwapi.proxy.messages.GameMessages.UnitIdOrBuilder>(
                  carrier_,
                  getParentForChildren(),
                  isClean());
          carrier_ = null;
        }
        return carrierBuilder_;
      }