(extenders protocol)
Returns a collection of the types explicitly extending protocol
user=> (defprotocol P (id [this]))
P
user=> (extend-protocol P
String
(id [this] this)
clojure.lang.Symbol
(id [this] (name this))
clojure.lang.Keyword
(id [this] (name this)))
nil
user=> (extenders P)
(java.lang.String clojure.lang.Symbol clojure.lang.Keyword)