Sets the root item for this model to the inputed item.
        
        :param      item | <XNavigationItem>

def setTopLevelItems( self, items ):
        """
        Sets the root item for this model to the inputed item.
        
        :param      item | <XNavigationItem>
        """
        self.blockSignals(True)
        
        root = self.invisibleRootItem()
        for row in range(root.rowCount()):
            root.takeRow(row)
        
        for item in items:
            root.appendRow(item)
            
        self.blockSignals(False)