sum over multiple dimensions gives "objects of type AFArray not callable"

`sum(::AFArray; dims::Tuple)` is defined but gives:
```
julia> sum(ones(AFArray,2,5),dims=(1,2))
ERROR: MethodError: objects of type AFMatrix{Float64} are not callable
Use square brackets [] for indexing an Array.
```
I believe it is defaulting to `sum(f, a; kw...)` and treating the AFArray as a function