Streaming data source plugin - query method - observable

Trying to emulate and extend the sample streaming data source plugin, using WebSockets and rxJs Observables. Unable to return an Observable from the query method.

Type ‘Observable’ is not assignable to type ‘Promise | Observable’.

Property ‘query’ in type ‘DataSource’ is not assignable to the same property in base type ‘DataSourceApi<MyQuery, MyDataSourceOptions>’.

Type ‘(options: DataQueryRequest) => Observable’ is not assignable to type ‘(request: DataQueryRequest) => Promise | Observable’.