source fb-marketing: add comment (#15812)

Author: davydov-d

airbyte-integrations/connectors/source-facebook-marketing/source_facebook_marketing/streams/async_job.py

@@ -22,6 +22,11 @@
 logger = logging.getLogger("airbyte")
 
 
+# `FacebookBadObjectError` occurs in FB SDK when it fetches an inconsistent or corrupted data.
+# It still has http status 200 but the object can not be constructed from what was fetched from API.
+# Also, it does not happen while making a call to the API, but later - when parsing the result,
+# that's why a retry is added to `get_results()` instead of extending the existing retry of `api.call()` with `FacebookBadObjectError`.
+
 backoff_policy = retry_pattern(backoff.expo, FacebookBadObjectError, max_tries=5, factor=5)