@Override
            public void visitElement(@NotNull PsiElement element) {
                if (element instanceof QNameElement) {
                    final PsiReference[] references = element.getReferences();
                    for (PsiReference reference : references) {
                        if (reference instanceof PrefixReference prefixReference) {
                          if (prefixReference.isUnresolved()) {
                                prefixes.add(prefixReference.getPrefix());
                            }
                        }
                    }
                }
                super.visitElement(element);
            }
@Override
            public void visitElement(@NotNull PsiElement element)