@classmethod
def all(cls, client):
    """
        fetch all option positions
        """
    url = 'https://api.robinhood.com/options/events/'
    params = {}
    data = client.get(url, params=params)
    results = data['results']
    while data['next']:
        data = client.get(data['next'])
        results.extend(data['results'])
    return results
