onWalletSnapshot ({ cbGID }, cb) {
    this._registerListener('ws', null, Wallet, cbGID, cb)
  }
Register a handler to be called on each wallet snapshot (sent on auth)

@param {object} opts - options
@param {string} [opts.cbGID] - callback group id
@param {Function} cb - callback
@see https://docs.bitfinex.com/v2/reference#ws-auth-wallets