.Fluxautosizefor

			autosizefor(::Type, x)

If an _ in your layer's constructor, used within @autosize, should not mean the 2nd-last dimension, then you can overload this.

For instance autosizefor(::Type{<:Dense}, x::AbstractArray) = size(x, 1) is needed to make @autosize (2,3,4) Dense(_ => 5) return Dense(2 => 5) rather than Dense(3 => 5).