QObject::findChildren() strange behavior

[folibis]

In my program I have QDialog to edit configuration options and it is empty as program start.
I use QPlugin modules so each module can add its own panel to this dialog. Base class of such panel is:

class ConfigWidget : public QWidget
{
public:
    explicit ConfigWidget(QWidget *parent = 0) : QWidget(parent){}
    virtual void SetValues(){}
    virtual void SaveValues(){}
};

class ConfigWidget : public QWidget
{
public:
    explicit ConfigWidget(QWidget *parent = 0) : QWidget(parent){}
    virtual void SetValues(){}
    virtual void SaveValues(){}
};

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And the code of accept() signal of this dialog:

void ConfigDialog::okClicked()
{
    QList<ConfigWidget *> widgets = findChildren<ConfigWidget *>();
    foreach(ConfigWidget * widget,widgets)
    {
        widget->SaveValues();
    }
    Config::instance()->SaveConfig();
    accept();
}

void ConfigDialog::okClicked()
{
    QList<ConfigWidget *> widgets = findChildren<ConfigWidget *>();
    foreach(ConfigWidget * widget,widgets)
    {
        widget->SaveValues();
    }
    Config::instance()->SaveConfig();
    accept();
}

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I just get all the panels and save its values. I guess it is very simple and clear.
But findChildren returns all the widgets of dialog - buttons, lineedits etc. And it is very very strange for me.
From docs: Returns all children of this object with the given name that can be cast to type T
How QPushButton can be cast to ConfigWidget?? QPushButton have no SaveValues() function so I am very disappointed here ...
And, if it is expected result of findChildren(), how can I get only widgets derived from ConfigWidget?