code: @Override
      public Map<String, DataSource> getDataSources() {
          HashMap<String, DataSource> map = new HashMap<>();
          for (Map.Entry<String, HikariDataSource> entry : sources.entrySet()) {
              if (entry.getValue() != null) {
                  map.put(entry.getKey(), entry.getValue());
              }
          }
          return map;
      }
docs: Gets the set of data sources (name -> data source).
  It contains the available data sources only.
  
  @return the map of name -> data source, empty if none.