12. Scope Mechanism

tf中所有socpe的概念都是为了在其范围内定义一个统一的参数，使代码更加简洁。

12.1. name scope

Name scopes add a prefix to the name of all operations created in the same context., “the prefix”就是那个统一的参数

12.2. variable scope

Variable scopes add a prefix to the name of all Variables created in the same context.

12.3. arg scope

define arguments for a list of operations