watch method
Implementation
Stream<ChangeEvent> watch(Object pipeline,
        {int? batchSize,
        String? hint,
        Map<String, Object>? hintDocument,
        ChangeStreamOptions? changeStreamOptions,
        Map<String, Object>? rawOptions}) =>
    watchCursor(pipeline,
            batchSize: batchSize,
            hint: hint,
            hintDocument: hintDocument,
            changeStreamOptions: changeStreamOptions,
            rawOptions: rawOptions)
        .changeStream;