Allow N inputs

Add tests with `vcat`

src/layers/basic.jl

@@ -538,7 +538,7 @@ end
 
 This layer behaves differently based on input type:
 
-1. If input `x` is a tuple of length `N`, matching the number of `layers`, 
+1. If input `x` is a tuple of length N (or the input is `xs` with N `x`'s), matching the number of `layers`, 
   then each layer receives a new input `x[i]` combined with the previous output `y[i-1]` using `connection`.
   Thus `(y1, y2, y3) = PairwiseFusion(connection, layer1, layer2, layer3)((x1, x2, x3))`
   may be drawn as:
@@ -567,7 +567,7 @@ end
 
 ## Returns
 
-A tuple of length `N` with the output of each fusion ((`y1`, `y2`, ..., `yN`) in the example above).
+A tuple of length N with the output of each fusion ((`y1`, `y2`, ..., `yN`) in the example above).
 """
 struct PairwiseFusion{F, T<:Union{Tuple, NamedTuple}}
   connection::F
@@ -597,6 +597,7 @@ function (m::PairwiseFusion)(x::T) where {T}
   _pairwise_check(x, m.layers, T)
   applypairwisefusion(m.layers, m.connection, x)
 end
+(m::PairwiseFusion)(xs...) = m(xs)
 
 @generated function applypairwisefusion(layers::Tuple{Vararg{<:Any,N}}, connection, x::T) where {N, T}
   y_symbols = [gensym() for _ in 1:(N + 1)]

test/layers/basic.jl

@@ -365,4 +365,7 @@ end
   @test length(y) == 2
   @test size(y[1]) == (10, 10)
   @test size(y[2]) == (1, 10)
+
+  @test PairwiseFusion(vcat, x->x.+1, x->x.+2, x->x.^3)(2, 10, 20) == (3, [5, 12], [125, 1728, 8000])
+  @test PairwiseFusion(vcat, x->x.+1, x->x.+2, x->x.^3)(7) == (8, [10, 9], [1000, 729, 343])
 end