t() :: %ExOkex.Futures.Instrument{
  alias: String.t(),
  base_currency: String.t(),
  contract_val: String.t(),
  contract_val_currency: String.t(),
  delivery: String.t(),
  instrument_id: String.t(),
  is_inverse: String.t(),
  listing: String.t(),
  quote_currency: String.t(),
  settlement_currency: String.t(),
  tick_size: String.t(),
  trade_increment: String.t(),
  underlying: String.t(),
  underlying_index: String.t()
}