public Builder clearResearchedTechs() {
        if (researchedTechsBuilder_ == null) {
          researchedTechs_ = java.util.Collections.emptyList();
          bitField0_ = (bitField0_ & ~0x00100000);
          onChanged();
        } else {
          researchedTechsBuilder_.clear();
        }
        return this;
      }