From type/Metamodel/Primitives

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method set_parameterizer(Mu \obj, &parameterizer --> Nil)

Initializes the parameterization cache for a metaobject. This incorporates the &parameterize routine to produce parameterizations to be cached. This is assumed to carry a signature compatible with :(Mu $root, List:D $args), $root being the base metaobject for the parameterization, $args being the type arguments' object buffer.