Add @non_differentiable annotation to _adjacency_matrix function

Author: dferre97

GNNlib/ext/GNNlibCUDAExt.jl

@@ -4,6 +4,7 @@ using CUDA
 using Random, Statistics, LinearAlgebra
 using GNNlib: GNNlib, propagate, copy_xj, e_mul_xj, w_mul_xj
 using GNNGraphs: GNNGraph, COO_T, SPARSE_T, to_dense, to_sparse
+using ChainRulesCore: @non_differentiable
 
 const CUDA_COO_T = Tuple{T, T, V} where {T <: AnyCuArray{<:Integer}, V <: Union{Nothing, AnyCuArray}}
 
@@ -63,4 +64,6 @@ function _adjacency_matrix(g::GNNGraph{<:CUDA_COO_T}, T::DataType = eltype(g); d
     return dir == :out ? A : A'
 end
 
+@non_differentiable _adjacency_matrix(x...)
+
 end #module