docs: long storeSpaceForAdd() {
          return TreeMap.maximumSerializedSize() // Map header.
                 + 64 * TreeMap.Entry.maximumSerializedSize() // Balanced path.  
                 + 65 * owningToken.objectStore.getAddSpaceOverhead() // Store overhead for all of the above.
                 + storeSpaceForRemove(); // In case we backoutTheAdd.
      }