code: public StringColumn append(String value) {
          try {
              lookupTable.append(value);
          } catch (NoKeysAvailableException ex) {
              lookupTable = lookupTable.promoteYourself();
              try {
                  lookupTable.append(value);
              } catch (NoKeysAvailableException e) {
                  // this can't happen
                  throw new IllegalStateException(e);
              }
          }
          return this;
      }
docs: Added for naming consistency with all other columns