IterableIterator error in util/index.ts

[PrettyGoodFreedomTech]

When I run tsc calculateFromLibrary.ts on this file in Brainstorm, I get this error:

../../../node_modules/@graperank/util/index.ts:112:26 - error TS2802: Type 'IterableIterator<[Index2, Value]>' can only be iterated through when using the '--downlevelIteration' flag or with a '--target' of 'es2015' or higher.

112     array.push([key, [...value.entries()]])
                             ~~~~~~~~~~~~~~~


Found 1 error in ../../../node_modules/@graperank/util/index.ts:112

I haven't chased this down yet, just recording it here for now.