code: def add_oauth_header(self):
          
          # abort if no token
          oauth_token = self._get_token()
          if not oauth_token:
              return
  
          # add oauth header & reach the api
          self.headers["Authorization"] = "token " + oauth_token
          url = self._api_url("user")
          raw_resp = self.requests.get(url)
          resp = raw_resp.json()
  
          # abort & remove header if token is invalid
          if resp.get("login", None) != self.user:
              self.oops("Invalid token for user " + self.user)
              self.headers.pop("Authorization")
              return
  
          self.is_authenticated = True
          self.yeah("User {} authenticated".format(self.user))
docs: Validate token and add the proper header for further requests.
          :return: (None)