private static @Nullable PsiReference createSchemaPrefixReference(final PsiElement element) {
    if (element instanceof XmlAttributeValue attributeValue) {
      final String prefix = XmlUtil.findPrefixByQualifiedName(attributeValue.getValue());
      if (!prefix.isEmpty()) {
        return new SchemaPrefixReference(attributeValue, TextRange.from(1, prefix.length()), prefix, null);
      }
    }
    return null;
  }
private static @Nullable PsiReference createSchemaPrefixReference(final PsiElement element)