code: @Nullable
      public ByteIterable get2(@NotNull final Transaction txn, @NotNull final ByteIterable second) {
          return this.second.get(txn, second);
      }
docs: Search for the second entry in the second database. Use this method for databases configured with no duplicates.
  
  @param second second key (value for first).
  @return null if no entry found, otherwise the value.