In modeling terms, you would most usually expect to see a UML component here; however, such a restriction seems arbitrary, and so the metaclass is noted as class for more flexibility.

在建模的术语里，你可能最经常期望见到的一个UM L组件。然而，这样的一个约束似乎是武断的，所以为了更大的灵活性，元类被指明作为一个类。