如何在Pyqt中创建可调整大小的布局UI？

import sys
from PyQt5.QtWidgets import QApplication, QWidget, QVBoxLayout, QHBoxLayout, QPushButton

class MyWindow(QWidget):
    def __init__(self):
        super().__init__()

        # 创建垂直布局
        layout = QVBoxLayout()

        # 创建水平布局
        sub_layout = QHBoxLayout()

        # 创建按钮
        button1 = QPushButton("Button 1")
        button2 = QPushButton("Button 2")

        # 将按钮添加到水平布局中
        sub_layout.addWidget(button1)
        sub_layout.addWidget(button2)

        # 将水平布局添加到垂直布局中
        layout.addLayout(sub_layout)

        # 设置布局
        self.setLayout(layout)

        # 设置窗口大小可调整
        self.setFixedSize(300, 200)
        self.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Expanding)

if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = MyWindow()
    window.show()
    sys.exit(app.exec_())