[basex-talk] Problem with serialize function and use-character-maps option

When I try

serialize("This is a test with a slash / Test.", map { 'method' : 'json', 'use-character-maps' : map { '/' : '/'}})

with BaseX 8.6.4 is indicates an error [SEPM0017] Invalid 'use-character-maps' value 'map { "/": "/" }'; must be a string.

However, the W3C spec https://www.w3.org/TR/xpath-functions-31/#func-serialize suggests the syntax is use-character-maps map(xs:string, xs:string)? with "For the use-character-maps option, the value is a map, whose keys are the characters to be mapped (as xs:string instances), and whose corresponding values are the strings to be substituted for these characters.".

So it seems BaseX is not implementing the finalized spec here.