DEFINITION arity_sred_wcpr0_pr0()
TYPE =
       ∀g:G.∀c1:C.∀t1:T.∀a:A.(arity g c1 t1 a)→∀c2:C.(wcpr0 c1 c2)→∀t2:T.(pr0 t1 t2)→(arity g c2 t2 a)
BODY =
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