Will the following complex show optical isomerism So there is this question which asks whether the following complex 


  $\ce{[Co(NH3)4Br2]+}$ 


will show optical  isomerism or not.

According to my knowledge it will show optical isomerism in cis form only and not in trans form so overall the compound shouldn’t be optically active.

This what I hav been taught. And moreover shouldn’t it be optically active in every scenario to be called so?

But the ans says that it shows optical isomerism.
I don’t understand why.. is my understanding wrong?
As already commented by Ivan Neretin, the cis form also does not show optical isomerism. Elaborating a bit further on the comments: 

Complexes show optical isomerism when they are asymmetric (also known as chiral). They should not have any elements of symmetry, such as planes/axes/centres of symmetry. The trans form has a clearly visible plane of symmetry. It's a bit trickier to find the plane for the cis form. Here's a diagram showing the planes:

(source: Chemistry libretexts)