◊(Local Yarn Code "Diff")

(define doc 
  '(root (p "If I had been astonished at first catching a glimpse of so outlandish an "
            "individual as Queequeg circulating among the polite society of a civilized "
            "town, that astonishment soon departed upon taking my first daylight "
            "stroll through the streets of New Bedford…")))
(default-title (get-elements doc))]

@defproc[(series-pagenode) pagenode?]
@defproc[(metas-series-pagenode) pagenode?]

If @code{(current-metas)} has the key @racket['series], converts its value to the pagenode pointing to
that series, otherwise returns @racket['||].

@defproc[(series-noun) string?]
@defproc[(series-metas-noun) string?]

If @code{(current-metas)} has the key @racket['series], and if the corresponding series defines a meta
value for @racket['noun-singular], then return it, otherwise return @racket[""].

@defproc[(series-title) string?]
@defproc[(series-metas-title) string?]

If @code{(current-metas)} has the key @racket['series], and if the corresponding series defines a meta
value for @racket['title], then return it, otherwise return @racket[""].

@defproc[(invalidate-series) (or/c void? boolean?)]

If the current article specifies a @racket['series] meta, and if a corresponding @filepath{.poly.pm}