Removes the dependency between the this item and the inputed target.
        
        :param      item | <XGanttWidgetItem>

def takeDependency(self, item):
        """
        Removes the dependency between the this item and the inputed target.
        
        :param      item | <XGanttWidgetItem>
        """
        if ( not item in self._dependencies ):
            return
        
        item._reverseDependencies.pop(self)
        viewItem = self._dependencies.pop(item)
        
        scene    = viewItem.scene()
        if ( scene ):
            scene.removeItem(viewItem)