python - Forcing QgsTask to cancel in QGIS plugin?

I want to force closing Qgis project (QgsTask) in some point

NOTE:
QgsProject.instance().clear() # NOT WORKING

QgsTaskManager().cancelAll() # NOT WORKING

QgsTask.cancel() # NOT WORKING

task.canCancel() # FALSE

project = QgsProject.instance()
project.clear() # NOT WORKING

QgsTaskManager().cancelAll() # NOT WORKING
tasks = QgsApplication.taskManager().activeTasks()
for task in tasks:
    print (task.canCancel()) # False
    print (task.description()) # Loading “C:/Users/User/Desktop/some_project.qgs”
    print (task.flags()) # 

    task.cancel() # NOT WORKING

Is there any way to force closing project or task or change flag QgsTask.CanCancel to True ?