def create_lookup_url(usernames, user_fields):
    """
    Parameters
    ----------
    usernames : str
        Username that you want to search.
        => Sample: usernames=TwitterDev <=

    user_fields : str
        User fields are adjustable, options include:
        created_at, description, entities, id, location, name,
        pinned_tweet_id, profile_image_url, protected,
        public_metrics, url, username, verified, and withheld
        => Sample: user.fields=description,created_at <=
    """
    url = "https://api.twitter.com/2/users/by?{}&{}".format(
        usernames, user_fields)
    return url