He meant
julia> using SparseArrays
julia> A = spzeros(20,0)
20×0 SparseMatrixCSC{Float64, Int64} with 0 stored entries
He meant
julia> using SparseArrays
julia> A = spzeros(20,0)
20×0 SparseMatrixCSC{Float64, Int64} with 0 stored entries