private com.google.protobuf.SingleFieldBuilder<
          org.bwapi.proxy.messages.GameMessages.UnitType, org.bwapi.proxy.messages.GameMessages.UnitType.Builder, org.bwapi.proxy.messages.GameMessages.UnitTypeOrBuilder> 
          getCenterFieldBuilder() {
        if (centerBuilder_ == null) {
          centerBuilder_ = new com.google.protobuf.SingleFieldBuilder<
              org.bwapi.proxy.messages.GameMessages.UnitType, org.bwapi.proxy.messages.GameMessages.UnitType.Builder, org.bwapi.proxy.messages.GameMessages.UnitTypeOrBuilder>(
                  center_,
                  getParentForChildren(),
                  isClean());
          center_ = null;
        }
        return centerBuilder_;
      }