docs(async): mark new AsyncIO APIs as experimental

Author: sinhasubham

google/cloud/spanner_v1/_async/batch.py

@@ -50,6 +50,7 @@
 DEFAULT_RETRY_TIMEOUT_SECS = 30
 
 
+# Experimental API - Please note that this API is currently experimental and can change in the future.
 class _BatchBase(_SessionWrapper):
     """Accumulate mutations for transmission during :meth:`commit`.
 

google/cloud/spanner_v1/_async/client.py

@@ -167,6 +167,7 @@ def _initialize_metrics(project, credentials):
                     )
 
 
+# Experimental API - Please note that this API is currently experimental and can change in the future.
 class Client(ClientWithProject):
     """Client for interacting with Cloud Spanner API.
 

google/cloud/spanner_v1/_async/database.py

@@ -115,6 +115,7 @@
 DEFAULT_RETRY_BACKOFF = AsyncRetry(initial=0.02, maximum=32, multiplier=1.3)
 
 
+# Experimental API - Please note that this API is currently experimental and can change in the future.
 class Database(object):
     """Representation of a Cloud Spanner Database.
 

google/cloud/spanner_v1/_async/instance.py

@@ -81,6 +81,7 @@ def _type_string_to_type_pb(type_string):
 
 
 @CrossSync.convert_class(add_mapping_for_name="Instance")
+# Experimental API - Please note that this API is currently experimental and can change in the future.
 class Instance(object):
     """Representation of a Cloud Spanner Instance.
 

google/cloud/spanner_v1/_async/pool.py

@@ -73,6 +73,7 @@ async def __aexit__(self, exc_type, exc_value, traceback):
 
 
 @CrossSync.convert_class
+# Experimental API - Please note that this API is currently experimental and can change in the future.
 class AbstractSessionPool(object):
     """Specifies required API for concrete session pool implementations.
 
@@ -209,6 +210,7 @@ def session(self, **kwargs):
 
 
 @CrossSync.convert_class
+# Experimental API - Please note that this API is currently experimental and can change in the future.
 class FixedSizePool(AbstractSessionPool):
     """Concrete session pool implementation:
 
@@ -475,6 +477,7 @@ async def clear(self):
 
 
 @CrossSync.convert_class
+# Experimental API - Please note that this API is currently experimental and can change in the future.
 class BurstyPool(AbstractSessionPool):
     """Concrete session pool implementation:
 
@@ -586,6 +589,7 @@ async def clear(self):
 
 
 @CrossSync.convert_class
+# Experimental API - Please note that this API is currently experimental and can change in the future.
 class PingingPool(FixedSizePool):
     """Concrete session pool implementation:
 
@@ -835,6 +839,7 @@ async def ping(self):
 
 
 @CrossSync.convert_class
+# Experimental API - Please note that this API is currently experimental and can change in the future.
 class TransactionPingingPool(PingingPool):
     """Concrete session pool implementation:
 

google/cloud/spanner_v1/_async/session.py

@@ -48,6 +48,7 @@
 
 
 @total_ordering
+# Experimental API - Please note that this API is currently experimental and can change in the future.
 class Session(object):
     """Representation of a Cloud Spanner Session.
 

google/cloud/spanner_v1/_async/snapshot.py

@@ -776,6 +776,7 @@ def _update_for_precommit_token_pb_unsafe(
             self._precommit_token = precommit_token_pb
 
 
+# Experimental API - Please note that this API is currently experimental and can change in the future.
 class Snapshot(_SnapshotBase):
     """Allow a set of reads / SQL statements with shared staleness."""
 

google/cloud/spanner_v1/_async/streamed.py

@@ -23,6 +23,7 @@
 from google.cloud.spanner_v1.types.type import TypeCode
 
 
+# Experimental API - Please note that this API is currently experimental and can change in the future.
 class StreamedResultSet(object):
     """Process a sequence of partial result sets into a single set of row data.
 

google/cloud/spanner_v1/_async/transaction.py

@@ -54,6 +54,7 @@
 from google.cloud.spanner_v1.types.transaction import TransactionOptions
 
 
+# Experimental API - Please note that this API is currently experimental and can change in the future.
 class Transaction(_SnapshotBase, _BatchBase):
     """Implement read-write transaction semantics for a session.
 

google/cloud/spanner_v1/batch.py

@@ -243,7 +243,7 @@ def wrapped_method():
                     max_commit_delay=max_commit_delay,
                     request_options=request_options,
                 )
-                call_metadata, error_augmenter = database.with_error_augmentation(
+                (call_metadata, error_augmenter) = database.with_error_augmentation(
                     getattr(database, "_next_nth_request", 0), 1, metadata, span
                 )
                 commit_method = functools.partial(