private void ensureRequiredUnitsIsMutable() {
        if (!((bitField0_ & 0x00000040) == 0x00000040)) {
          requiredUnits_ = new java.util.ArrayList<org.bwapi.proxy.messages.GameMessages.UnitTypeIntPair>(requiredUnits_);
          bitField0_ |= 0x00000040;
         }
      }