onAccountTradeUpdate ({ symbol, cbGID }, cb) {
    this._registerListener('auth-tu', { 1: symbol }, Trade, cbGID, cb)
  }
Register a handler to be called on each personal trade `'tu'` event

@param {object} opts - options
@param {string} [opts.pair] - required if no symbol specified
@param {string} [opts.symbol] - required if no pair specified
@param {string|number} [opts.cbGID] - callback group id
@param {Function} cb - callback
@see https://docs.bitfinex.com/v2/reference#ws-auth-trades