A data scientist has computed updated rows containing new feature values for primary keys already stored in the Feature Store table 'features'. The updated feature values are stored in the DataFrame 'features_df'. They aim to update the rows in 'features' if the associated primary key is in 'features_df'. If a row's primary key is not in 'features_df', they want the row to remain unchanged in 'features'. Which code block using the Feature Store Client 'fs' accomplishes this task?