+ readable writable attr _visibility_level: Int = 1 # FIXME: why this should be defined ?
+
+ # Is the global class a mixin class?
+ # A mixin class inherits all constructors from a superclass
+ meth is_mixin: Bool
+ do
+ return _mixin_of != self
+ end
+
+ # Indicate the superclass the class is a mixin of.
+ # If mixin_of == self then the class is not a mixin
+ # Is two classes have the same mixin_of value, then they both belong to the same mixing group
+ readable writable attr _mixin_of: MMGlobalClass = self
+