This file describes the schemata used for notmuch's structured output
-format (currently JSON).
+format (currently JSON and S-Expressions).
[]'s indicate lists. List items can be marked with a '?', meaning
they are optional; or a '*', meaning there can be zero or more of that
alternates (e.g., int|string means something can be an int or a
string).
+For S-Expression output, lists are printed delimited by () instead of
+[]. Objects are printed as p-lists, i.e. lists where the keys and values
+are interleaved. Keys are printed as keywords (symbols preceded by a
+colon), e.g. (:id "123" :time 54321 :from "foobar"). Null is printed as
+nil, true as t and false as nil.
+
Common non-terminals
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