Add GPTJForQuestionAnswering (#14503)

* Add GPTJForQuestionAnswering

* Reformat for GPTJForQuestionAnswering

* Fix isort error

* make style for GPTJForQA

* Add _keys_to_ignore_on_load_missing

* Change the sequence of qa and classification

Co-authored-by: Suraj Patil <surajp815@gmail.com>

tests/test_modeling_gptj.py

@@ -32,6 +32,7 @@ if is_torch_available():
         GPTJ_PRETRAINED_MODEL_ARCHIVE_LIST,
         AutoTokenizer,
         GPTJForCausalLM,
+        GPTJForQuestionAnswering,
         GPTJForSequenceClassification,
         GPTJModel,
     )
@@ -356,7 +357,11 @@ class GPTJModelTester:
 @require_torch
 class GPTJModelTest(ModelTesterMixin, GenerationTesterMixin, unittest.TestCase):
 
-    all_model_classes = (GPTJModel, GPTJForCausalLM, GPTJForSequenceClassification) if is_torch_available() else ()
+    all_model_classes = (
+        (GPTJModel, GPTJForCausalLM, GPTJForSequenceClassification, GPTJForQuestionAnswering)
+        if is_torch_available()
+        else ()
+    )
     all_generative_model_classes = (GPTJForCausalLM,) if is_torch_available() else ()
     fx_ready_model_classes = all_model_classes
     test_pruning = False