Checks if the given keyCode is a modifier key. If it is, returns the modifier name
        constant as defined in the iomediator module. If not, returns C{None}

def __decodeModifier(self, keyCode):
        """
        Checks if the given keyCode is a modifier key. If it is, returns the modifier name
        constant as defined in the iomediator module. If not, returns C{None}
        """
        keyName = self.lookup_string(keyCode, False, False, False)
        if keyName in MODIFIERS:
            return keyName

        return None