code: func (r *RoleBindingBuilder) Binding() (RoleBinding, error) {
  	if len(r.RoleBinding.Subjects) == 0 {
  		return RoleBinding{}, fmt.Errorf("subjects are required: %#v", r.RoleBinding)
  	}
  
  	return r.RoleBinding, nil
  }
docs: // Binding builds and returns the RoleBinding API object from the builder
  // object.