Default type checker for 'object' seems too narrow

[benmaddison]

Is there a specific reason that jsonschema._types.is_object tests for instances of dict rather than the more generic alternative of collections.abc.Mapping?

Apologies if this has been asked and answered previously - I couldn't find it in the list of closed issues.

[Julian]

Hi there. Essentially as a balance, because isinstance on collections.abc.Mapping is quite slow for the majority case.

Obviously if you have a more generic thing you can certainly reconfigure your type checker.

Closing but lemme know if anything could use clarifying in the docs.