CSS-style not applied to first QSizeGrip of composite widget in QVBoxLayout

import sys
from PySide2 import QtCore
from PySide2.QtWidgets import QApplication, QWidget , QMainWindow , QGraphicsView , QVBoxLayout , QFrame , QSizeGrip , QWidget


class TestWidget(QWidget):
	def __init__(self , parent=None):
		super(TestWidget , self).__init__(parent)

		layout = QVBoxLayout()
		layout.setContentsMargins( 0 , 0 , 0 , 0 )

		frame = QFrame()
		frame.setFrameShape(QFrame.StyledPanel)
		frame.setMinimumHeight( 100 )

		grip = QSizeGrip(self)
		grip.setStyleSheet( "QSizeGrip { image: url(dots.png); }")
		grip.setCursor(QtCore.Qt.SplitVCursor)

		layout.addWidget(frame)
		layout.addWidget( grip , 0 , QtCore.Qt.AlignBottom | QtCore.Qt.AlignRight )

		self.setLayout(layout)

class TestApp(QMainWindow):
	def __init__(self, parent=None):
		super(TestApp, self).__init__(parent)

		track1 = TestWidget()
		track2 = TestWidget()
		track3 = TestWidget()

		centralWidget = QWidget()
		layout = QVBoxLayout(centralWidget)

		layout.addWidget(track1)
		layout.addWidget(track2)
		layout.addWidget(track3)

		self.setCentralWidget(centralWidget)
		self.show()	

if __name__=="__main__":
    app = QApplication(sys.argv)
    myapp = TestApp();
    sys.exit(app.exec_())