Returns the record item class instance linked with this tree widget.
        
        :return     <XOrbRecordItem>

def recordItemClass(self, record=None):
        """
        Returns the record item class instance linked with this tree widget.
        
        :return     <XOrbRecordItem>
        """
        if record is not None:
            key = type(record)
        else:
            key = None
        
        return self._recordItemClass.get(key, self._recordItemClass[None])