code: func (r *prefixedRegistrar) Find(entity DomainObject) (*RegisteredEntity, error) {
  	t := reflect.TypeOf(entity).Elem()
  	re, ok := r.typeIndex[t]
  	if !ok {
  		return nil, errors.Errorf("failed to find registration for entity %q", t.Name())
  	}
  	return re, nil
  }
docs: // Find looks at its internal index to find a registration that matches the
  // entity instance provided. Return an error when not found.