code: public char getKeyAsChar(int index) throws IOException {
          if (index >= structure.keySizes.size()) {
              throw new IOException("Index " + index + " is out of range.");
          }
  
          return Bytes.toChar(key, structure.keyByteOffsets.get(index));
      }
docs: Returns the key belonging to the given field as char
  
  @param index
  the index of the requested field
  @return the requested value
  @throws IOException