def already_in_league(user, player, mongo):
    """Check if a player already in the league

    Parameters:
        user: the user dictionary (dict)
        player: the player object
        mongo: the mongo db
    Returns
        taken: True if someone already taken that player, False otherwise
    """
    taken = True
    user = mongo.db.users.find_one({'pid': player['player_id']})
    if user is None:
        taken = False
    return taken