I want to build a discord bot, but can't install some dependencies using apt-get

The library I want to use :

I'd like to use the voice feature, but I'm unsure if :

  • libffi-dev (or libffi-devel on some systems)

  • python-dev (e.g. python3.5-dev for Python 3.5)

are installed on python anywhere. Can somebody help me ?

They're already installed.