The getter 'controller' isn't defined for the class 'BehaviorSubject'.

I get following error. Any idea how to fix it?
Thanks

"flight_details_bloc.dart",
"severity": 8,
"message": "The getter 'controller' isn't defined for the class 'BehaviorSubject'.\nTry importing the library that defines 'controller', correcting the name to the name of an existing getter, or defining a getter or field named 'controller'.",
"source": "dart",
"startLineNumber": 124,
"startColumn": 53,
"endLineNumber": 124,
"endColumn": 63,
"tags": []

Start by inspecting flight_details_bloc.dart around line 124 and identify how BehaviorSubject is being used. Run the Dart analyzer to reproduce the reported getter error, then trace the relevant BehaviorSubject API and verify that the analyzer reports no error after the intended correction.

Written by the indexing model from the issue text.