https://docs.google.com/document/d/1Ee4XL4TtTxojtkgRRetm4uIMAmiazH1CrA5Q6FKTlrM, specifically the part that says:

> Make subclasses rather than mixins.   For example, make Templated extend the Widget class, so that Templated subclasses classes (like Dialog) can just extend Templated, without mentioning Widget.   I thought this wasn't possible due to "multiple inheritance issues", but it turns out that it works with dojo.declare() (not sure about ComposeJS) and the behavior is well defined by C3MRO.