mixin lodash use concat "Confuse"

[HoKangInfo]

const list =[[1,2,3],[4,5,6]]
const cond = [0,1]

 _.chain(cond)
    .map((value, key) => list[key])
    .concat()
    .value()

but

 await _$.chain(cond)
    .map((value, key) => list[key])
    .concat() // need iterator function
    .value()

must

 await _$.chain(cond)
//    .map((value, key) => list[key])
    .concat((value, key) => list[key]) 
    .value()

[suguru03]

@HoKangInfo Thanks for the issue!
I need to investigate it but I could make it optional 😄