const YahooFantasy = require('yahoo-fantasy');
const yf = new YahooFantasy(
  Y!APPLICATION_KEY,
  Y!APPLICATION_SECRET,
  tokenCallbackFn, // optional
  redirectUri // optional
);

yf.setUserToken(
  Y!OAuthAccessToken
);

// promise based
try {
  const position_types = await yf.game.position_types(game_key);
} catch (e) {
  // handle error
}

// callback based
yf.game.position_types(game_key, callbackFn);

{
  "game_key": "331",
  "game_id": "331",
  "name": "Football",
  "code": "nfl",
  "type": "full",
  "url": "http://football.fantasysports.yahoo.com/f1",
  "season": "2014",
  "position_types": [
    {
      "type": "O",
      "display_name": "Offense"
    },
    {
      "type": "K",
      "display_name": "Kickers"
    },
    {
      "type": "DT",
      "display_name": "Defense/Special Teams"
    },
    {
      "type": "DP",
      "display_name": "Defensive Players"
    }
  ]
}