docs: private IndexableConstraint getClassFieldReaderForHashedAlpha(final AlphaNode alphaNode) throws IllegalArgumentException {
          final AlphaNodeFieldConstraint fieldConstraint = alphaNode.getConstraint();
  
          if (!(fieldConstraint instanceof IndexableConstraint)) {
              throw new IllegalArgumentException("Only support IndexableConstraint hashed AlphaNodes, not " + fieldConstraint.getClass());
          }
          // we need to get the first alpha in the map to get the attribute name that be use for the prefix of the
          // generated variable name
          return (IndexableConstraint) fieldConstraint;
      }