code: private void initChunkMap() {
          Statement stmt = null;
          Connection connection = null;
  
          try {
              Class.forName("org.sqlite.JDBC");
              connection = DriverManager.getConnection("jdbc:sqlite:" + databasePath);
  
              // retrieve chunk IDs from database
              String sql = "SELECT id, chromosome, start FROM chunk";
              stmt = connection.createStatement();
              ResultSet rs = stmt.executeQuery(sql);
              chunkIdMap = new HashMap<>();
              while (rs.next()) {
                  chunkIdMap.put(rs.getString("chromosome") + "_" + rs.getInt("start"), rs.getInt("id"));
              }
          } catch (SQLException e) {
              logger.error(e.getClass().getName() + ": " + e.getMessage());
              cleanConnectionClose(connection, stmt);
          } catch (ClassNotFoundException e) {
              logger.error(e.getClass().getName() + ": " + e.getMessage());
              e.printStackTrace();
          }
      }
docs: Initialize the map of chunks.