The bla bla part
After struggling a couple of hours to display the my vertical tabs, and searching on the internet for a description, I've found what was my mistake. This article's intention is to save time for those developers who has just encountered with this problem and wants to find a quick solution.
Sollution
Basically after examining the code example from the example module, I've found that the vertical_tabs are the container of the different fieldsets, and the title of the fieldset is the vertical tab's title.
All tabs are connected to the vertical_tabs through the #group attribute. It's that simple...
