code: public boolean delete(final Txn<T> txn, final T key) {
      return delete(txn, key, null);
    }
docs: Deletes the key using the passed transaction.
  
  @param txn transaction handle (not null; not committed; must be R-W)
  @param key key to delete from the database (not null)
  @return true if the key/data pair was found, false otherwise
  
  @see #delete(org.lmdbjava.Txn, java.lang.Object, java.lang.Object)