coAxiomArity :: CoAxiom br -> BranchIndex -> Arity
coAxiomArity ax index
  = length $ cab_tvs $ coAxiomNthBranch ax index
coAxiomArity :: CoAxiom br -> BranchIndex -> Arity
coAxiomArity ax index
  = length $ cab_tvs $ coAxiomNthBranch ax index
coAxiomArity ax index
  = length $ cab_tvs $ coAxiomNthBranch ax index