private static String getReferenceText(PyClass fromClass, PyClass toClass) {
    final PyExpression[] superClassExpressions = fromClass.getSuperClassExpressions();
    for (PyExpression expression : superClassExpressions) {
      if (expression instanceof PyReferenceExpression) {
        PsiElement target = ((PyReferenceExpression)expression).getReference().resolve();
        if (target == toClass) {
          return expression.getText();
        }
      }
    }
    return toClass.getName();
  }
private static String getReferenceText(PyClass fromClass, PyClass toClass)