@Nullable
  public static LookupElementBuilder buildFileLookupElement(PsiFile file, PsiFileSystemItem item, @Nullable Set<? super String> existingNames) {
    final String s = FileUtilRt.getNameWithoutExtension(item.getName());
    if (!PyNames.isIdentifier(s)) return null;
    if (existingNames != null) {
      if (existingNames.contains(s)) {
        return null;
      }
      else {
        existingNames.add(s);
      }
    }
    return PyCompletionUtilsKt.createLookupElementBuilder(file, item);
  }
@Nullable
  public static LookupElementBuilder buildFileLookupElement(PsiFile file, PsiFileSystemItem item, @Nullable Set<? super String> existingNames)