Support 'is mapping' as required by llama3.1 Instruct

[mattjcly]

Have run into an issue with huggingface/jinja and llama3.1 instruct's chat template.

This line from the chat template:

{%- if message.content is mapping or message.content is iterable %}

Results in error:

Unknown test: mapping

Have noticed this to be the case with both huggingface/jinja@0.3.0 and huggingface/jinja@0.3.1

Support for this test would be great to avoid the need to patch out this line!

[coyotte508]

cc @xenova maybe?