code: public boolean exists(long featureId, String database, String table) {
          boolean exists = false;
          Map<String, Map<Long, FeatureShape>> tables = databases.get(database);
          if (tables != null) {
  
              Map<Long, FeatureShape> featureIds = tables.get(table);
              if (featureIds != null) {
                  FeatureShape shapes = featureIds.get(featureId);
                  exists = shapes != null && shapes.hasShapes();
              }
          }
          return exists;
      }
docs: Check if map shapes exist for the feature id, database, and table
  
  @param featureId feature id
  @param database  GeoPackage database
  @param table     table name
  @return true if exists