How to use the @ethersproject/base64.encode function in @ethersproject/base64

}
        }

        if (connection.user != null && connection.password != null) {
            if (url.substring(0, 6) !== "https:" && connection.allowInsecureAuthentication !== true) {
                logger.throwError(
                    "basic authentication requires a secure https url",
                    Logger.errors.INVALID_ARGUMENT,
                    { argument: "url", url: url, user: connection.user, password: "[REDACTED]" }
                );
            }

            let authorization = connection.user + ":" + connection.password;
            headers["authorization"] = {
                key: "Authorization",
                value: "Basic " + base64Encode(toUtf8Bytes(authorization))
            };
        }
    }

    return new Promise(function(resolve, reject) {

        let timer: any = null;
        if (timeout) {
            timer = setTimeout(() => {
                if (timer == null) { return; }
                timer = null;

                reject(logger.makeError("timeout", Logger.errors.TIMEOUT, { timeout: timeout }));
            }, timeout);
        }

if (connection.headers) {
            for (var key in connection.headers) {
                headers[key.toLowerCase()] = { key: key, value: String(connection.headers[key]) };
                if (["if-none-match", "if-modified-since"].indexOf(key.toLowerCase()) >= 0) {
                    allow304 = true;
                }
            }
        }
        if (connection.user != null && connection.password != null) {
            if (url.substring(0, 6) !== "https:" && connection.allowInsecureAuthentication !== true) {
                logger.throwError("basic authentication requires a secure https url", logger_1.Logger.errors.INVALID_ARGUMENT, { argument: "url", url: url, user: connection.user, password: "[REDACTED]" });
            }
            var authorization = connection.user + ":" + connection.password;
            headers["authorization"] = {
                key: "Authorization",
                value: "Basic " + base64_1.encode(strings_1.toUtf8Bytes(authorization))
            };
        }
    }
    if (json) {
        options.method = "POST";
        options.body = json;
        headers["content-type"] = { key: "Content-Type", value: "application/json" };
    }
    var flatHeaders = {};
    Object.keys(headers).forEach(function (key) {
        var header = headers[key];
        flatHeaders[header.key] = header.value;
    });
    options.headers = flatHeaders;
    var runningTimeout = (function () {
        var timer = null;

if (connection.headers) {
            for (const key in connection.headers) {
                headers[key.toLowerCase()] = { key: key, value: String(connection.headers[key]) };
                if (["if-none-match", "if-modified-since"].indexOf(key.toLowerCase()) >= 0) {
                    allow304 = true;
                }
            }
        }
        if (connection.user != null && connection.password != null) {
            if (url.substring(0, 6) !== "https:" && connection.allowInsecureAuthentication !== true) {
                logger.throwError("basic authentication requires a secure https url", Logger.errors.INVALID_ARGUMENT, { argument: "url", url: url, user: connection.user, password: "[REDACTED]" });
            }
            const authorization = connection.user + ":" + connection.password;
            headers["authorization"] = {
                key: "Authorization",
                value: "Basic " + base64Encode(toUtf8Bytes(authorization))
            };
        }
    }
    if (json) {
        options.method = "POST";
        options.body = json;
        headers["content-type"] = { key: "Content-Type", value: "application/json" };
    }
    const flatHeaders = {};
    Object.keys(headers).forEach((key) => {
        const header = headers[key];
        flatHeaders[header.key] = header.value;
    });
    options.headers = flatHeaders;
    const runningTimeout = (function () {
        let timer = null;