Make combobox items checkable(multi-selection) in Mari

Coding
,
1

I want to populate a combobox with udims of current geometry and I also want to make it checkable.
I have applied a model to combobox as a data. Here’s my code

from PySide.QtGui import *
from PySide.QtCore import *

cmb = QComboBox()
udims = [udim.name() for udim in mari.current.geo().patchList() ]
model = StandardItemModel(len(udims), 1)
for i, udim in enumerate(udims):
    item = QStandardItem(udim)
    item.setFlags(Qt.ItemIsUserCheckable | ItemIsEnabled)
    item.setData(Qt.Checked | Qt.CheckStateRole)
    model.setItem(item)

cmb.setModel(model)

Behavior of combox is changed but no checkbox is visible nor the items are selectable. I can’t figure out what’s the problem.