neovim doesn't show expansion "list" of completions

Question

In this example, when class is typed, a list of potential expansions is shown. The snippet itself works in my nvim, but the list is not shown.

Commenting out my whole init.vim (the vimrc of neovim), just leaving the Ultisnip installation hasn't changed anything.

=> What is the vim name for that "list" ? How do i fix this? What could i look for to debug it?

Answer 1

I just overlooked the part of the description

[...] In this demo I am editing a python file. I first expand the #! snippet, then the class snippet. The completion menu comes from YouCompleteMe,[...]