class[['x, 'i, 'o]]
tx :('x, 'i, 'o) wire ->
object
..end
Cf_state_gadget.connector
A wire carrying messages of type 'x
.method put : 's. 'x -> ('s, 'i, 'o, unit) t
tx#put obj
to schedule the message obj for deliver on the
associated wire.