isPermissions method Null safety

1. baguette
2. PermissionManager
3. PermissionManager
4. isPermissions method

PermissionManager class

1. Constructors
2. PermissionManager
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. addPlugin
8. askPermissions
9. cleanPlugins
10. getPlugin
11. isPermissions
12. noSuchMethod
13. removePlugin
14. toString
15. Operators
16. operator ==