private addToHttpParams(httpParams: HttpParams, value: any, key?: string): HttpParams {
    if (typeof value === "object" && value instanceof Date === false) {
        {{#isQueryParamObjectFormatJson}}
        httpParams = httpParams.append(key, JSON.stringify(value));
        {{/isQueryParamObjectFormatJson}}
        {{^isQueryParamObjectFormatJson}}
        httpParams = this.addToHttpParamsRecursive(httpParams, value);
        {{/isQueryParamObjectFormatJson}}
    } else {
        httpParams = this.addToHttpParamsRecursive(httpParams, value, key);
    }
    return httpParams;
}

private addToHttpParamsRecursive(httpParams: HttpParams, value?: any, key?: string): HttpParams {
    if (value == null) {
        return httpParams;
    }

    if (typeof value === "object") {
        if (Array.isArray(value)) {
            (value as any[]).forEach( elem => httpParams = this.addToHttpParamsRecursive(httpParams, elem, key));
        } else if (value instanceof Date) {
            if (key != null) {
                httpParams = httpParams.append(key,
                    (value as Date).toISOString(){{^isDateTime}}.substr(0, 10)){{/isDateTime}};
            } else {
                throw Error("key may not be null if value is Date");
            }
        } else {
            Object.keys(value).forEach( k => httpParams = this.addToHttpParamsRecursive(
                httpParams, value[k], key != null ? `${key}{{#isQueryParamObjectFormatDot}}.{{/isQueryParamObjectFormatDot}}{{#isQueryParamObjectFormatKey}}[{{/isQueryParamObjectFormatKey}}${k}{{#isQueryParamObjectFormatKey}}]{{/isQueryParamObjectFormatKey}}` : k));
        }
    } else if (key != null) {
        httpParams = httpParams.append(key, value);
    } else {
        throw Error("key may not be null if value is not object or array");
    }
    return httpParams;
}