def api_url(domain):
    """Returns the Freshbooks API URL for a given domain.
    
        >>> api_url('billing.freshbooks.com')
        'https://billing.freshbooks.com/api/2.1/xml-in'
    """
    return "https://%s/api/2.1/xml-in" % (domain, )
dataset/ETHPy150Open freshbooks/refreshbooks/refreshbooks/api.py/api_url/original