code: protected Map<String, AttributeValue> untransformAttributes(String hashKey, String rangeKey,
              Map<String, AttributeValue> attributeValues) {
          return attributeValues;
      }
docs: Transforms the attribute values after loading from DynamoDb.
  Only ever called by {@link #untransformAttributes(Class, Map)}.
  By default, returns the attributes unchanged. Currently, the
  values associated with the hash key and range key must be left unchanged.
  
  @param hashKey the attribute name of the hash key
  @param rangeKey the attribute name of the range key (or null if there is none)
  @param attributeValues
  @return the decrypted attributes