code: function getHistoricalClosePrices(options = {}) {
    const { index, currency, start, end, yesterday } = options
  
    return request(`/historical/close.json`, {
      index,
      currency,
      start: start && end && formatDate(start) || undefined,
      end: start && end && formatDate(end) || undefined,
      for: yesterday ? 'yesterday' : undefined
    })
  }
docs: memoize 1' TTL 15"