code: @CheckResult protected Observable<Integer> update(@NonNull final String table,
        @NonNull final ContentValues values, @Nullable final String whereClause,
        @Nullable final String... whereArgs) {
      return Observable.defer(new Func0<Observable<Integer>>() {
        @Override
        public Observable<Integer> call() {
          return Observable.just(db.update(table, values, whereClause, whereArgs));
        }
      });
    }
docs: Update rows
  
  @param table The table to update
  @param values The values to update
  @param whereClause The where clause
  @param whereArgs The where clause arguments
  @return An <b>deferred</b> observable containing the number of rows that have been changed by this update