Use of prismatic schema =>

Question

What is the intended use of the => macro?

https://github.com/plumatic/schema/blob/master/src/cljx/schema/core.cljx#L1077-L1091

It seems to pass as long as a function is passed, for instance:

(s/defschema MySchema s/Int)

(def a (s/=> MySchema s/Num))

(s/validate a :ok)