docs: func (s *Shape) IsRequired(member string) bool {
  	ref, ok := s.MemberRefs[member]
  	if !ok {
  		panic(fmt.Sprintf(
  			"attempted to check required for unknown member, %s.%s",
  			s.ShapeName, member,
  		))
  	}
  	if ref.IdempotencyToken || ref.Shape.IdempotencyToken {
  		return false
  	}
  	if ref.Location == "uri" || ref.HostLabel {
  		return true
  	}
  	for _, n := range s.Required {
  		if n == member {
  			return true
  		}
  	}
  	return false
  }