[{"time":[[1,2,3],[2,3,4],[4,5,6]],"bar":[[2,5,9,8],[6,3,7,"None"],[7,8,"None"]]}]

db.collection.aggregate([{$project:{time:{$reduce:{input:"$time",initialValue:[],in:{$setUnion:["$$value","$$this"]}}},bar:{$filter:{input:{$reduce:{input:"$bar",initialValue:[],in:{$setUnion:["$$value","$$this"]}}},cond:{$ne:["$$this","None"]}}}}}])