code: @NonNull
      public static As database(@NonNull com.couchbase.lite.Database database) {
          if (database == null) {
              throw new IllegalArgumentException("database cannot be null.");
          }
          return new As(database);
      }
docs: Create a database as a data source.
  
  @param database the database used as a source of data for query.
  @return {@code DataSource.Database} object.