@Nullable
  private static PyType getBaseStringType(@NotNull PsiElement referenceTarget) {
    final PyBuiltinCache builtinCache = PyBuiltinCache.getInstance(referenceTarget);
    if (referenceTarget instanceof PyElement && builtinCache.isBuiltin(referenceTarget) &&
        PyNames.BASESTRING.equals(((PyElement)referenceTarget).getName())) {
      return builtinCache.getStrOrUnicodeType(true);
    }
    return null;
  }
@Nullable
  private static PyType getBaseStringType(@NotNull PsiElement referenceTarget)