markPrice: Get mark price

curl 'https://api.poloniex.com/markets/BTC_USDT/markPrice'

import requests

resp = requests.get("https://api.poloniex.com/markets/BTC_USDT/markPrice")
data = resp.json()

import zingu_apis

api = zingu_apis.api("poloniex")
result = api.fetch("markets/{symbol}/markPrice")

for item in result:
    print(item)

const resp = await fetch("https://api.poloniex.com/markets/BTC_USDT/markPrice");
const data = await resp.json();