docs(v3): update the doc on diagnostic info

google/cloud/dialogflowcx_v3/types/session.py

@@ -800,10 +800,27 @@ class QueryResult(proto.Message):
             Intent match result, could be an intent or an
             event.
         diagnostic_info (google.protobuf.struct_pb2.Struct):
-            The free-form diagnostic info. For example,
-            this field could contain webhook call latency.
-            The string keys of the Struct's fields map can
-            change without notice.
+            The free-form diagnostic info. For example, this field could
+            contain webhook call latency. The fields of this data can
+            change without notice, so you should not write code that
+            depends on its structure.
+
+            One of the fields is called "Alternative Matched Intents",
+            which may aid with debugging. The following describes these
+            intent results:
+
+            -  The list is empty if no intent was matched to end-user
+               input.
+            -  Only intents that are referenced in the currently active
+               flow are included.
+            -  The matched intent is included.
+            -  Other intents that could have matched end-user input, but
+               did not match because they are referenced by intent
+               routes that are out of
+               `scope <https://cloud.google.com/dialogflow/cx/docs/concept/handler#scope>`__,
+               are included.
+            -  Other intents referenced by intent routes in scope that
+               matched end-user input, but had a lower confidence score.
         sentiment_analysis_result (google.cloud.dialogflowcx_v3.types.SentimentAnalysisResult):
             The sentiment analyss result, which depends on
             [``analyze_query_text_sentiment``]