docs: func (s *Shape) PayloadRefName() string {
  	if name := s.Payload; len(name) != 0 {
  		// Root shape
  		return name
  	}
  
  	for name, ref := range s.MemberRefs {
  		if ref.IsEventPayload {
  			return name
  		}
  	}
  
  	return ""
  }