I'm using PYQT for developing an application. my requirement is to insert a tree view with checkbox inside a combobox items. I would like to know how to achieve this?

I have the following code but this does not work.

```
class CheckboxInsideListbox(QWidget):
def __init__(self, parent = None):
    super(CheckboxInsideListbox, self).__init__(parent)
    self.setGeometry(250,250,300,300)
    self.MainUI()

def MainUI(self):
    #stb_label = QLabel("Select STB\'s")
    stb_combobox = QComboBox()

    length = 10
    cb_layout = QVBoxLayout(stb_combobox)
    for i in range(length):
        c = QCheckBox("STB %i" % i)
        cb_layout.addWidget(c)

    main_layout = QVBoxLayout()
    main_layout.addWidget(stb_combobox)
    main_layout.addLayout(cb_layout)

    self.setLayout(main_layout)

```

Please let me know if I'm missing anything here.