public static Hop parse(String str) {
        Route route = Route.parse(str);
        if (route.getNumHops() > 1) {
            return new Hop().addDirective(new ErrorDirective("Failed to completely parse '" + str + "'."));
        }
        return route.getHop(0);
    }
Parses the given string as a single hop. The {@link #toString()}
method is compatible with this parser.

@param str The string to parse.
@return A hop that corresponds to the string.
messagebus/src/main/java/com/yahoo/messagebus/routing/Hop.java