Could be: arc> (= codes {("Boston" 'bos) ("San Francisco" 'sfo) ("Paris" 'cdg)} {("Boston" 'bos) ("San Francisco" 'sfo) ("Paris" 'cdg)}
If the () are required or not is up for discussion, keys/values could be positional like obj.
Note that printing (obj a 1 b 2) as (obj a 1 b 2) is ambiguous with printing the list '(obj a 1 b 2)
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