Only look at attributes implementing Annotation

[mathroc]

Q	A
Bug fix?	yes
New feature?	no
BC breaks?	no
Deprecations?	no
Tests pass?	yes/no
Documented?	no
Fixed tickets	#...
License	MIT

This make the code slightly more efficient as it avoids instantiating unrelated attributes and also prevents crashes in case some attributes cannot be instantiated

[Vincz]

@mathroc If you can fix the coding standard (just run the composer command), I'll merge it !