docs: TypeConverter getConverter(String attributeName) {
          Object attributeValue = getAttributeValue(attributeName);
          if (attributeValue == null) {
              return NULL_CONVERTER;
          } else if (attributeValue instanceof MultiResult) {
              MultiResult multiResult = (MultiResult) attributeValue;
              for (Object result : multiResult.getResults()) {
                  if (result != null) {
                      AttributeType attributeType = extractAttributeType(result);
                      return attributeType == null ? IDENTITY_CONVERTER : attributeType.getConverter();
                  }
              }
              return NULL_CONVERTER;
          } else {
              AttributeType attributeType = extractAttributeType(attributeValue);
              return attributeType == null ? IDENTITY_CONVERTER : attributeType.getConverter();
          }
      }