Return **True** if the start- and end position denote valid
        positions within the document.

        |Args|

        * ``selPos`` (**tuple**): tuple with four integers.

        |Returns|

        **bool**: **True** if the positions are valid; **False** otherwise.

        |Raises|

        * **None**

def isSelectionPositionValid(self, selPos: tuple):
        """
        Return **True** if the start- and end position denote valid
        positions within the document.

        |Args|

        * ``selPos`` (**tuple**): tuple with four integers.

        |Returns|

        **bool**: **True** if the positions are valid; **False** otherwise.

        |Raises|

        * **None**
        """
        if selPos is None:
            return False
        if len(selPos) != 4:
            return False
        check1 = self.isPositionValid(*selPos[:2])
        check2 = self.isPositionValid(*selPos[2:])
        if check1 and check2:
            return True
        else:
            return False