[tune] Allow fetching pinned objects from trainable functions (#1895)

* updates

* lint

* Update util.py

* Update function_runner.py

* updates

python/ray/tune/function_runner.py

@@ -9,6 +9,7 @@ import traceback
 from ray.tune import TuneError
 from ray.tune.trainable import Trainable
 from ray.tune.result import TrainingResult
+from ray.tune.util import _serve_get_pin_requests
 
 
 class StatusReporter(object):
@@ -108,6 +109,7 @@ class FunctionRunner(Trainable):
                             self._default_config["script_min_iter_time_s"]))
         result = self._status_reporter._get_and_clear_status()
         while result is None:
+            _serve_get_pin_requests()
             time.sleep(1)
             result = self._status_reporter._get_and_clear_status()
         if result.timesteps_total is None: