Flax T5 (#12150)

* copy pytorch-t5

* init

* boom boom

* forward pass same

* make generation work

* add more tests

* make test work

* finish normal tests

* make fix-copies

* finish quality

* correct slow example

* correct slow test

* version table

* upload models

* Update tests/test_modeling_flax_t5.py

* correct incorrectly deleted line

Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>
Co-authored-by: Patrick von Platen <patrick@huggingface.co>

tests/test_modeling_flax_bart.py

@@ -72,7 +72,7 @@ def prepare_bart_inputs_dict(
     }
 
 
-class FlaxBartModelTester(unittest.TestCase):
+class FlaxBartModelTester:
     def __init__(
         self,
         parent,

tests/test_modeling_t5.py

@@ -794,6 +794,21 @@ class T5ModelIntegrationTests(unittest.TestCase):
     def tokenizer(self):
         return T5Tokenizer.from_pretrained("t5-base")
 
+    @slow
+    def test_small_generation(self):
+        model = T5ForConditionalGeneration.from_pretrained("t5-small").to(torch_device)
+        model.config.max_length = 8
+        model.config.num_beams = 1
+        model.config.do_sample = False
+        tokenizer = T5Tokenizer.from_pretrained("t5-small")
+
+        input_ids = tokenizer("summarize: Hello there", return_tensors="pt").input_ids
+
+        sequences = model.generate(input_ids)
+
+        output_str = tokenizer.batch_decode(sequences, skip_special_tokens=True)[0]
+        self.assertTrue(output_str == "Hello there!")
+
     @slow
     def test_small_integration_test(self):
         """