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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def onShortcutUnindentWithBackspace(self):
 """Backspace pressed, unindent """

        assert self._qpart.textBeforeCursor().endswith(self.text())

        charsToRemove = len(self._qpart.textBeforeCursor()) % len(self.text())
        if charsToRemove == 0:
            charsToRemove = len(self.text())

        cursor = self._qpart.textCursor()
        cursor.setPosition(cursor.position() - charsToRemove, QTextCursor.KeepAnchor)
        cursor.removeSelectedText()