IronRuby.StandardLibrary.Yaml.Emitter.prepareTagHandle C# (CSharp) Method

        static string prepareTagHandle(string handle) {
            if (string.IsNullOrEmpty(handle)) {
                throw new EmitterException("tag handle must not be empty");
            } else if (handle[0] != '!' || handle[handle.Length-1] != '!') {
                throw new EmitterException("tag handle must start and end with '!': " + handle);
            } else if ("!" != handle && !HANDLE_FORMAT.IsMatch(handle)) {
                throw new EmitterException("invalid syntax for tag handle: " + handle);
            }
            return handle;
        }