async def fetch_order_book(self, symbol, limit=None, params={}):
    (await self.load_markets())
    market = self.market(symbol)
    request = {'symbol': market['id']}
    if (limit is not None):
        request['limit'] = limit
    response = (await self.marketGetDepth(self.extend(request, params)))
    timestamp = self.safe_value(response, 'timestamp')
    orderbook = self.parse_order_book(response, symbol, timestamp)
    return orderbook
async def fetch_order_book(self, symbol, limit=None, params={}):
    (await self.load_markets())
    market = self.market(symbol)
    request = {'symbol': market['id']}
    if (limit is not None):
        request['limit'] = limit
    response = (await self.marketGetDepth(self.extend(request, params)))
    timestamp = self.safe_value(response, 'timestamp')
    orderbook = self.parse_order_book(response, symbol, timestamp)
    return orderbook