Adjust FIXME and add to README

Author: lpsinger

README.md

@@ -6,3 +6,8 @@ Use optimistic locking to put DynamoDB records with auto-incrementing attributes
 
 - https://aws.amazon.com/blogs/aws/new-amazon-dynamodb-transactions/
 - https://bitesizedserverless.com/bite/reliable-auto-increments-in-dynamodb/
+
+## FIXME
+
+This package currently depends on code that is in a pull request for boto3 that is not yet merged or released.
+See https://github.com/boto/boto3/pull/4010.

dynamodb_autoincrement.py

@@ -55,7 +55,7 @@ def put(self, item: DynamoDBItem):
                     self._put_item(**put)
             else:
                 try:
-                    # FIXME: depends on unreleased code in boto3.
+                    # FIXME: depends on an unmerged PR for boto3.
                     # See https://github.com/boto/boto3/pull/4010
                     self.dynamodb.transact_write_items(  # type: ignore[attr-defined]
                         TransactItems=[{"Put": put} for put in puts]