CreateGroupRequest does not implement the visibility property properly (?)

[magelfik]

Hi there, first of all thank you for the work you are sharing with everybody !

I have found something I am not sure I understand : In the CreateGroupRequest class, the visibility property seems to accept a bool type : should'nt it accept a String type such as "private", "public", or "internal" ?

The v4 of the api seem to only accept these settings. I am using the 4.0.0-snapshot of your API and I'm trying to create a private group.

I am sorry in advance if I misunderstood the main use of this class.

Thank you in advance for your answer.