@NotNull
  public static PyExpression getFirstQualifier(@NotNull PyQualifiedExpression expr) {
    final PyExpression qualifier = expr.getQualifier();
    if (qualifier instanceof PyQualifiedExpression) {
      return getFirstQualifier((PyQualifiedExpression)qualifier);
    }
    return expr;
  }
@NotNull
  public static PyExpression getFirstQualifier(@NotNull PyQualifiedExpression expr)