'Return the tokens needed to authenticate the access to any API the
service might provide. Trello uses a pair of OAuthToken consisting
on a oauth_token and oauth_token_secret.
instance must be a UserSocialAuth instance.'

@classmethod
def tokens(cls, instance):

    token = super(TrelloBackend, cls).tokens(instance)
    if (token and ('access_token' in token)):
        token = dict((tok.split('=') for tok in token['access_token'].split('&')))
    return token
