How to use the proxy-addr function in proxy-addr

ipProxyMiddleware(socket, next) {
        if (!socket.context) socket.context = {};

        try {
            socket.handshake.connection = {
                remoteAddress: socket.handshake.address
            };

            socket.context.ipAddress = proxyaddr(
                socket.handshake,
                this.proxyTrustFn
            );

            if (!socket.context.ipAddress) {
                throw new Error(
                    `Assertion failed: unexpected IP ${socket.context.ipAddress}`
                );
            }
        } catch (error) {
            LOGGER.warn('Rejecting socket - proxyaddr failed: %s', error);
            next(new Error('Could not determine IP address'));
            return;
        }

        if (isTorExit(socket.context.ipAddress)) {

public get ip() {
    return proxyAddr(this, SETTINGS["trust.proxy"]);
  }

function readProxyHeaders(trustFn, req, res, next) {
    const forwardedIP = proxyaddr(req, trustFn);
    if (forwardedIP !== req.ip) {
        req.realIP = forwardedIP;
        req.realProtocol = getForwardedProto(req);
    } else {
        req.realIP = req.ip;
        req.realProtocol = req.protocol;
    }

    next();
}

public ip (): string {
    const ipFn = this._config.getIp
    if (typeof (ipFn) === 'function') {
      return ipFn(this)
    }

    return proxyaddr(this.request, this._config.trustProxy)
  }