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()
def getAp3(self):
        ret = math.acos(((self.getLenp1() * self.getLenp1() + self.getLenp2() * self.getLenp2()) - self.getLenp3() * self.getLenp3()) / (2* self.getLenp1() * self.getLenp2()))
        return ret