code: func (a *AttributeDefinition) IsFile(attName string) bool {
  	if !a.Type.IsObject() {
  		panic("checking pointer field on non-object") // bug
  	}
  	att := a.Type.ToObject()[attName]
  	if att == nil {
  		return false
  	}
  	return att.Type.Kind() == FileKind
  }
docs: // IsFile returns true if the attribute is of type File or if any its children attributes (if any) is.