anchor.diff:        (cond
           ((keywordp list-type)
            ;; It is a primitive type like :string, :boolean, etc
  -         (loop for elem in input
  +         (loop for elem in (coerce input 'list)
               do
                 (add-list-member "ITEM" elem
                                  :serializer serializer
  
positive.code:         ((symbolp list-type)
           ;; It is a reference to a schema like 'user-schema'
           (let ((schema (find-schema list-type)))
             (loop for elem in input
                do
                  (with-list-member ("ITEM" :serializer serializer
                                            :stream stream)
  
negative.code:         ((listp list-type)
           ;; It is some compound type, like :object, :list, or :option
           (let ((schema list-type))
             (loop for elem in (coerce input 'list)
                do
                  (with-list-member ("ITEM" :serializer serializer
                                            :stream stream)
  