In Symbolics "Differentiation with array expressions is not yet supported" #14
Description
Symbolics distinguishes between symbolic arrays and "arrays of symbolic expressions", the later being called with Symbolics.variables. When I use the former I get the error "Differentiation with array expressions is not yet supported". Perhaps we could use Symbolics.variables for now in e.g. https://github.com/JuliaGNI/SymbolicNeuralNetworks.jl/blob/main/src/symbolic_neuralnet.jl.