/usr/lib/swipl/library/ext/json/http/http_json.pl
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 json_type(?MediaType) is semidet[multifile, library(http/http_json)]
True if MediaType is a JSON media type. http_json:json_type/1 is a multifile predicate and may be extended to facilitate non-conforming clients.
Arguments:
MediaType- is a term Type/SubType, where both Type and SubType are atoms.