title: Python PyQt6 resizing layouts QGridLayout
body: <p>I'm moving code over to the PyQt6 GUI framework.  And I'm learning.  But, I've hit a snag.  I can't set the geometry of a QGridLayout widget.  This code doesn't work, why?</p>
  <pre><code>class MainGUI(qt.QWidget):
      def __init__(self):
          super().__init__()
          self.lc_wig = None
          self.mailboxes = misc.read_mailboxes()
          test = qt.QLabel('testing...')
          self.grid_main = qt.QGridLayout()
          self.grid_main.setGeometry(QtCore.QRect(100, 100, 1000, 1000))
          self.grid_main.setContentsMargins(0, 0, 0, 0)
          self.grid_main.addWidget(test, 0, 0)
          self.setLayout(self.grid_main)
  
  app = qt.QApplication(sys.argv)
  main_gui = gui.MainGUI()
  main_gui.show()
  sys.exit(app.exec())
  </code></pre>
  <p>With the above code, I just get a small window with the &quot;testing...&quot; label placed in it.  How can I set the geometry of the layout?</p>