方法返回一个具有此视图名的单元素集合。
Method returns a single-element collection of this one view name .
罗素希望不通过计数，而是通过相等的概念，来定义单元素集合，
Russell wanted to define a set-with-one-element , without appealing to a concept of counting , by the idea of equality .
单元素集合