Returns the bounding rectangle for the inputed nodes.
        
        :param      nodes | [<XNode>, ..]

def calculateBoundingRect(self, nodes):
        """
        Returns the bounding rectangle for the inputed nodes.
        
        :param      nodes | [<XNode>, ..]
        """
        out = QRectF()
        for node in nodes:
            rect = node.rect()
            pos = node.pos()
            
            bounding = QRectF(pos.x(), pos.y(), rect.width(), rect.height())
            out = out.united(bounding)
        
        return out