Updated the get_policy API in the index_management plugin to allow the policy_id argument as optional (#633)

Signed-off-by: saimedhi <[email protected]>

opensearchpy/plugins/index_management.py

@@ -55,14 +55,14 @@ class IndexManagementClient(NamespacedClient):
         )
 
     @query_params()
-    def get_policy(self, policy: Any, params: Any = None, headers: Any = None) -> Any:
+    def get_policy(
+        self, policy: Any = None, params: Any = None, headers: Any = None
+    ) -> Any:
         """
-        Gets the policy by `policy_id`.
+        Gets the policy by `policy_id`; returns all policies if no policy_id is provided.
 
         :arg policy: The name of the policy
         """
-        if policy in SKIP_IN_PATH:
-            raise ValueError("Empty value passed for a required argument 'policy'.")
 
         return self.transport.perform_request(
             "GET",