Documentation for method compose_type assembled from the following pages:
Class: Metamodel::Primitives §
(Metamodel::Primitives) method compose_type §
method compose_type(Mu , )
Composes $type (that is, finalizes it to be ready for instantiation). See https://github.com/Raku/nqp/blob/master/docs/6model/repr-compose-protocol.markdown for what $configuration can contain (until we have better docs, sorry).