Currently cellFoldValues_F has a check that the data to be processed is made of all boolean values. However, the scalar counterpart, traverseF, can return non boolean values (e.g. when it is applied to a non-array value and the lambda returns non-boolean, i.e. Nothing) or handle non boolean values coming from the lambda (that are treated as "false")

e.g.

coll.aggregate([
            { $match: { "time": { $in: [[new Date("2019-09-27T21:14:45.654Z")]] } } }, { $group: { _id: null } }]
        )