from PySide6.QtWidgets import QApplication, QMainWindow, QWidget, QGridLayout, QVBoxLayout, QGraphicsDropShadowEffect, QLabel
from PySide6.QtGui import QPalette, QColor


class VerticalPaneWithShadow(QWidget):

    def __init__(self):
        super(VerticalPaneWithShadow, self).__init__()
        self.setAutoFillBackground(True)

        effect = QGraphicsDropShadowEffect(self, blurRadius=5)
        self.setGraphicsEffect(effect)

        layout = QVBoxLayout()
        layout.addWidget(QLabel("some"))
        layout.addWidget(QLabel("text"))
        layout.addWidget(QLabel("inside"))
        self.setLayout(layout)


class MainWindow(QMainWindow):

    def __init__(self):
        super(MainWindow, self).__init__()

        layout = QGridLayout()

        widget = VerticalPaneWithShadow()
        layout.addWidget(widget)

        main_widget = QWidget()
        main_widget.setLayout(layout)
        self.setCentralWidget(main_widget)


app = QApplication()

window = MainWindow()
window.show()

app.exec()