Right usage of second argument in proxy

What is the right way to use htt(p|ps) in second argument within proxy when I make a requests to a https site? The proxy I used below is just a placeholder.

When I try like this (it works):

proxies = {
  'https': 'http://79.170.192.143:34394',
}

when I try like this (it works as well):

proxies = {
  'https': 'https://79.170.192.143:34394',
}

Is the second htt(p|ps) in proxy just a placeholder and What if I make a requests to a http site?

from Right usage of second argument in proxy