getTreeFromFlatData set rootKey as null

[yongjiaaaa]

The function getTreeFromFlatData requires setting rootKey as null for it to work. However, the type of rootKey is set as string | number | undefined, resulting in a type error: Type 'null' is not assignable to type 'string | number | undefined'.ts(2322).

Can someone help to take a look?

code snippet:

    const treeItems = await import("react-sortable-tree").then(treeLib => {
      return treeLib.getTreeFromFlatData({
        flatData,
        getKey: node => node.id,
        getParentKey: node => node.parentId,
        // tslint:disable-next-line:no-null-keyword
        rootKey: null // The value of the parent key when there is no parent (i.e., at root level)
      });