Extending meta-schema

[hellozyemlya]

Sorry for posting this to the issues, moving to discussions.

The particular goal I have is adding additional value to "type" schema keyword.
There were suggestions that metaschema is a regular dictionary and can be modified, but how to locate that specific dictionary.
As far as I see type values comes from {'anyOf': [{'$ref': '#/$defs/simpleTypes'}, {'type': 'array', 'items': {'$ref': '#/$defs/simpleTypes'}, 'minItems': 1, 'uniqueItems': True}]} schema, but I can't get where to find its dictionary or how I can override/extend it.

Is that possible to define my own version of $defs/simpleType and make sure it used instead of original one?