how to add custom fonts into it

[Suv00m]

I've been trying to add custom fonts to it but due to some reasons it is not possible I don't know why

here is what I've tried :

from PySide6.QtGui import QFont, QFontDatabase, QFontMetrics
from PySide6.QtWidgets import QApplication, QWidget, QLabel

QFontDatabase.addApplicationFont("Bitlingvedas-Regular.ttf")

to add it into the system from which Pyside can access it but still, movis can't register it to the fonts list maybe it is the problem of threading I don't know please help me

and again the class is properly initiated in my code.