@classmethod
def add_url(cls, url, parent_id=0, callback_url=None):
    """ Add new transfer from URI"""
    data = {'url': url, 'save_parent_id': parent_id}
    if callback_url:
        data['callback_url'] = callback_url
    d = cls.client.request('/transfers/add', method='POST', data=data)
    return cls(d['transfer'])
