removing horovod from tf policy

ml-agents/mlagents/tf_utils/globals.py

 
 def get_rank() -> Optional[int]:
     return _rank
-
-
-def broadcast_variables() -> bool:
-    return True if _rank is not None else False

ml-agents/mlagents/trainers/policy/tf_policy.py

-from typing import Any, Dict, List, Optional, Tuple
+from typing import Any, Dict, List, Optional, Tuple, Callable
 import numpy as np
 from distutils.version import LooseVersion
 
     GaussianDistribution,
     MultiCategoricalDistribution,
 )
-from mlagents.tf_utils.globals import get_rank, broadcast_variables
+from mlagents.tf_utils.globals import get_rank
 
 
 logger = get_logger(__name__)
     Contains a learning model, and the necessary
     functions to save/load models and create the input placeholders.
     """
+
+    broadcast_global_variables: Callable[[int], None] = lambda x: None
 
     def __init__(
         self,
         else:
             self._initialize_graph()
         # broadcast initial weights from worker-0
-        if broadcast_variables():
-            self.sess.run(hvd.broadcast_global_variables(0))
+        TFPolicy.broadcast_global_variables(0)
 
     def get_weights(self):
         with self.graph.as_default():