You can search for identifiers within the package.
in-package search v0.2.0
module M : sig ... end
val lift : ('a, 'b) t -> ('a M.t, 'b M.t) t
lift eq produces a proof that 'a M.t and 'b M.t are equivalent if 'a and 'b are equivalent
lift eq
'a M.t
'b M.t
'a
'b