qtextcursor setposition doesn't work

[doc_symbiosis]

but in line 5, I have

cursor.setPosition(QTextCursor::Start,QTextCursor::MoveAnchor);

cursor.setPosition(QTextCursor::Start,QTextCursor::MoveAnchor);

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I also tried the following line instead:

cursor.setPosition(0);

cursor.setPosition(0);

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