Emitting signal when project property is changed using PyQGIS

QGIS API provides QgsExpressionContextUtils to set project properties.

But in the class, there isn’t any signal.

I hope to connect to a signal whenever some of the properties were changed.

So is there a way to implement this?

def my_slot():
    print("A project variable was just changed!")

QgsProject.instance().customVariablesChanged.connect(my_slot)