How to set Stylesheet specifically for a derived QProgressDialog

[ZXfkSIE]

I am programming under Qt 6.2 and have a derived QProgressDialog called TP_ProgressDialog.
I've tried following sheet codes:

TP_ProgressDialog { background-color: rgb(0,0,0); }
QProgressDialog { background-color: rgb(0,0,0); }
QDialog { background-color: rgb(0,0,0); }

but none of them works.

[ZXfkSIE]

OK I have fixed it.
I wrote color: white; before the specific sheet codes,
which seems to make TP_ProgressDialog { background-color: rgb(0,0,0); } invalid.