code: def get_vboxes(self):
          
          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
docs: Get the maximum ID of the VBoxes
  
          :return: Maximum VBox ID
          :rtype: int