You can search for identifiers within the package.
in-package search v0.2.0
derive_plugin
Derive_plugin.Derive
val start_deriving : Names.Id.t -> Constrexpr.constr_expr -> Names.Id.t -> Declare.Proof.t
start_deriving f suchthat lemma starts a proof of suchthat (which can contain references to f) in the context extended by f:=?x. When the proof ends, f is defined as the value of ?x and lemma as the proof.
start_deriving f suchthat lemma
suchthat
f
f:=?x
?x
lemma