
  [;1m-spec is_function(Term, Arity) -> boolean()[0m
  [;1m                     when Term :: term(), Arity :: arity().[0m

  Returns [;;4mtrue[0m if [;;4mTerm[0m is a fun that can be applied with [;;4mArity[0m
  number of arguments, otherwise [;;4mfalse[0m.

  Allowed in guard tests.
