for example (the sum must be 1.0). <double> x 9 : M3 Model (tv,tr,mt) x 3 set the probability to observe a transversion (tv), a transition (tr) or a match (mt) on each codon position (equivalent to 3 Bernoulli models). <double> x 27 : M14 Model (Pr(w) with w in {tv,tr,mt}^3)