Add Flax example tests (#14599)

* add test for glue

* add tests for clm

* fix clm test

* add summrization tests

* more tests

* fix few tests

* add test for t5 mlm

* fix t5 mlm test

* fix tests for multi device

* cleanup

* ci job

* fix metric file name

* make t5 more robust

examples/flax/text-classification/run_flax_glue.py

@@ -15,6 +15,7 @@
 # limitations under the License.
 """ Finetuning a 🤗 Flax Transformers model for sequence classification on GLUE."""
 import argparse
+import json
 import logging
 import os
 import random
@@ -522,6 +523,13 @@ def main():
             if args.push_to_hub:
                 repo.push_to_hub(commit_message=f"Saving weights and logs of epoch {epoch}", blocking=False)
 
+    # save the eval metrics in json
+    if jax.process_index() == 0:
+        eval_metric = {f"eval_{metric_name}": value for metric_name, value in eval_metric.items()}
+        path = os.path.join(args.output_dir, "eval_results.json")
+        with open(path, "w") as f:
+            json.dump(eval_metric, f, indent=4, sort_keys=True)
+
 
 if __name__ == "__main__":
     main()