Error in AsymmetricEnge derivatives

I found a bug in the AsymmetricEnge derivatives. Should be like:

f(x) = E(x-x0) + E(-x-x0) - 1
f^{(2n)} = E^{(2n)}(x-x0) + E^{(2n)}(-x-x0)
f^{(2n+1)} = E^{(2n)}(x-x0) - E^{(2n)}(-x-x0)

but I forgot to include the higher derivatives code.