Add gemma 2 (#31659)

* inital commit

* Add doc

* protect?

* fixup stuffs

* update tests

* fix build documentation

* mmmmmmm config attributes

* style

* nit

* uodate

* nit

* Fix docs

* protect some stuff

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Co-authored-by: Lysandre <lysandre@huggingface.co>

tests/test_modeling_common.py

@@ -505,7 +505,7 @@ class ModelTesterMixin:
 
         # Check that the parameters are equal.
         for p1, p2 in zip(model_low_usage.parameters(), model_non_low_usage.parameters()):
-            self.assertEquals(p1.data.ne(p2.data).sum(), 0)
+            self.assertEqual(p1.data.ne(p2.data).sum(), 0)
 
         # Check that the state dict keys are equal.
         self.assertEqual(set(model_low_usage.state_dict().keys()), set(model_non_low_usage.state_dict().keys()))