"<key>",
                JavaReflectionUtil.extractNestedType((TypeToken<Map<?, ?>>) node, Map.class, 1));
        }

        @SuppressWarnings("unchecked")
        @Override
        protected void walkNestedIterable(TypeToken<?> node, String qualifiedName, BiConsumer<String, TypeToken<?>> handler) {
            TypeToken<?> nestedType = JavaReflectionUtil.extractNestedType((TypeToken<? extends Iterable<?>>) node, Iterable.class, 0);

        if (Map.class.isAssignableFrom(propertyMetadata.getDeclaredType().getRawType())) {
            Class<?> keyType = JavaReflectionUtil.extractNestedType((TypeToken<Map<?, ?>>) propertyMetadata.getDeclaredType(), Map.class, 0).getRawType();
            NestedValidationUtil.validateKeyType(validationContext, propertyMetadata.getPropertyName(), keyType);
        }
    }

     * @param parameterizedClass the parameterized class
     * @param typeParameterIndex the index of the parameter
     * @return a TypeToken
     */
    public static <T> TypeToken<?> extractNestedType(TypeToken<T> beanType, Class<? super T> parameterizedClass, int typeParameterIndex) {
        ParameterizedType type = (ParameterizedType) beanType.getSupertype(parameterizedClass).getType();