[nfc] alias tf_agents.policies.policy_saver as tf_policy_saver (google#528)

Author: cnaples79

compiler_opt/rl/policy_saver.py

@@ -21,7 +21,7 @@
 
 import tensorflow as tf
 from tf_agents.policies import tf_policy
-from tf_agents.policies import policy_saver
+from tf_agents.policies import policy_saver as tf_policy_saver
 from tf_agents.typing import types as tf_agents_types
 
 OUTPUT_SIGNATURE = 'output_spec.json'
@@ -158,8 +158,8 @@ def __init__(self, policy_dict: dict[str, tf_policy.TFPolicy]):
       policy_dict: A dict mapping from policy name to policy.
     """
     self._policy_saver_dict: dict[str, tuple[
-        policy_saver.PolicySaver, tf_policy.TFPolicy]] = {
-            policy_name: (policy_saver.PolicySaver(
+        tf_policy_saver.PolicySaver, tf_policy.TFPolicy]] = {
+            policy_name: (tf_policy_saver.PolicySaver(
                 policy, batch_size=1, use_nest_path_signatures=False), policy
                          ) for policy_name, policy in policy_dict.items()
         }