Get the maximum ID of the VBoxes

        :return: Maximum VBox ID
        :rtype: int

def get_vboxes(self):
        """
        Get the maximum ID of the VBoxes

        :return: Maximum VBox ID
        :rtype: int
        """
        vbox_list = []
        vbox_max = None
        for node in self.nodes:
            if node['type'] == 'VirtualBoxVM':
                vbox_list.append(node['vbox_id'])

        if len(vbox_list) > 0:
            vbox_max = max(vbox_list)
        return vbox_max