* Escape the system message spliced into predefined chat templates
get_chat_template(..., system_message = ...) substitutes the message into a
{system_message} placeholder that sits inside a Jinja string literal in all 15
predefined templates that carry one, so a quote closes the literal and a
backslash is read as an escape:
vicuna "Answer the user's question." -> TemplateSyntaxError
vicuna r"Put it in \boxed{}." -> renders '\x08oxed{}'
vicuna r"C:\Users\me" -> TemplateSyntaxError
Reuse the escaper PR #7731 added for construct_chat_template, promoted to a
module-level _escape_jinja_literal and extended to escape double quotes so the
one helper covers llama-3.1's "..." literal as well as the '...' the rest use.
Apply it to the predefined branch of _change_system_message and to the ShareGPT
mapping values, and drop the hand-escaping from the two vicuna defaults, which
would otherwise be escaped twice.
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* Tighten the escaping comments
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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
