async def fetch_open_orders(self, symbol=None, since=None, limit=None, params={}):
    request = {'openClosed': 'OPEN'}
    return (await self.fetch_orders(symbol, since, limit, self.extend(request, params)))
async def fetch_open_orders(self, symbol=None, since=None, limit=None, params={}):
    request = {'openClosed': 'OPEN'}
    return (await self.fetch_orders(symbol, since, limit, self.extend(request, params)))