Creating a derived reducer for a DynMapReducer

const reducer = getContext("reducer");
  let derived = [];

  if (enableGrouping) {
      const filters = filterBy[compendiumType];
      const property = `system.${groupBy[compendiumType]}`;

      for (const filterValue of filters) {
          const dr = $reducer.derived.create(`${filterValue}`);
          console.log(dr);

          dr.filters.add((doc) => doc[property] === filterValue);
          derived.push(dr);
      }

      derived = derived;
  }