module S2:sig..end
type('a, 'b, 'c)writer ='a Type_class.writer0 -> ('b, 'c) Type_class.S1.writer
type('a, 'b, 'c)reader ='a Type_class.reader0 -> ('b, 'c) Type_class.S1.reader
type('a, 'b, 'c)t ='a Type_class.t0 -> ('b, 'c) Type_class.S1.t