Are only certain drafts of JSON schemas supported by quicktype? If so, which?

[grahamalama]

Update:
Turns out my specific problem was related to the malformed schema and not quicktype, but I am still curious if there's an answer to the title of this post.

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I'm trying to generate Dart classes for this GBFS JSON schema specification, and quicktype seems to be having trouble with it:

> quicktype https://raw.githubusercontent.com/MobilityData/gbfs-json-schema/0e3651f2c03f41c2dc8cb2852a020e37f90f42d5/system_hours.json --src-lang schema --out system_hours.dart                

Issue in line 69: quicktype cannot infer this type because there is no data about it in the input.
69:     dynamic userTypes;

Issue in line 70: quicktype cannot infer this type because there is no data about it in the input.
70:     dynamic days;

Issue in line 71: quicktype cannot infer this type because there is no data about it in the input.
71:     dynamic startTime;

Issue in line 72: quicktype cannot infer this type because there is no data about it in the input.
72:     dynamic endTime;

Yet, it would appear there is information about those types contained within the schema. Is quicktype not able to "find" those definitions because of an issue with supporting certain JSON schema drafts? Or maybe something about the nested nature of this schema is throwing things off?