public boolean isBuiltin(@Nullable PsiElement target) {
    if (target == null) return false;
    PyPsiUtils.assertValid(target);
    if (!target.isValid()) return false;
    final PsiFile the_file = target.getContainingFile();
    if (!(the_file instanceof PyFile)) {
      return false;
    }
    // files are singletons, no need to compare URIs
    return the_file == myBuiltinsFile || the_file == myExceptionsFile;
  }
public boolean isBuiltin(@Nullable PsiElement target)