python-mode: ensure t or nil?

[buhtz]

Dear David,

in your Python IDE video you explained to use ensure nil to make sure that the currently installed (emacs in build?) pytho mode is used instead of the one on MELPA.

But in your Emacs.org file here in this repo the ensure is set to t not nil.

(use-package python-mode
  :ensure t

Do I misunderstood something?