QTextEdit or QTextDocument toHtml() doesn't evaluate correct blockCount when QTextFrameFormat of rootFrame (in this case, margin) is changed.

# -*- coding: utf-8 -*-
from PySide2 import QtCore, QtGui, QtWidgets
import PySide2
import os, sys
dirname = os.path.dirname(PySide2.__file__)
plugin_path = os.path.join(dirname, 'plugins', 'platforms')
os.environ['QT_QPA_PLATFORM_PLUGIN_PATH'] = plugin_path
class MyEdit(QtWidgets.QTextEdit):
    def __init__(self, parent=None):
        super(MyEdit, self).__init__(parent)
        document = self.document() 
        rootFrame = document.rootFrame()
        rootFrameFormat = rootFrame.frameFormat()
        rootFrameFormat.setLeftMargin(30.5)
        rootFrameFormat.setRightMargin(30.5)
        rootFrameFormat.setTopMargin(30.5)
        rootFrameFormat.setBottomMargin(30)
        rootFrame.setFrameFormat(rootFrameFormat)
        self.setHtml(self.toHtml())#You can see that an extra block is added when you push cursor ↓.
        #An extra block is added every loading (in my application), so it results in being many empty blocks at the end of QTextDocument before I know it.
        #For the sake of first aid, I check the blockcount before and after, if blockcount is changed, I delete the end block.
 
def main():
 
    app = QtWidgets.QApplication(sys.argv) if QtWidgets.QApplication.instance() is None else QtWidgets.QApplication.instance()
    textedit = MyEdit()
    textedit.show()
    sys.exit(app.exec_())
if __name__ == "__main__":
    main()