function Cookie(cookiestr, request_domain, request_path) {
	        if (cookiestr instanceof Cookie) {
	            return cookiestr;
	        }
	        if (this instanceof Cookie) {
	            this.name = null;
	            this.value = null;
	            this.expiration_date = Infinity;
	            this.path = String(request_path || "/");
	            this.explicit_path = false;
	            this.domain = request_domain || null;
	            this.explicit_domain = false;
	            this.secure = false; //how to define default?
	            this.noscript = false; //httponly
	            if (cookiestr) {
	                this.parse(cookiestr, request_domain, request_path);
	            }
	            return this;
	        }
	        return new Cookie(cookiestr, request_domain, request_path);
	    }
Save the cookies in the given `res` to
the agent's cookie jar for persistence.

@param {Response} res
@api private