AccountManagerKey constructor Null safety

1. baguette
2. AccountManagerKey
3. AccountManagerKey
4. AccountManagerKey constructor

AccountManagerKey class

1. Constructors
2. AccountManagerKey
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. toString
9. Operators
10. operator ==
11. Constants
12. TAG
13. UPDATE_ACCOUNT