[Misc] Add gemma3 chat template with pythonic-style function calling

[philipchung]

This PR adds a Jinja2 chat prompt template for Gemma-3 for generating tool calls in pythonic format and is compatible with the existing vLLM pythonic tool call parser that extracts the tool calls and formats them into the tool_calls field for ChatCompletion responses as a ChatCompletionMessageToolCall.

The template is a combination of contributions from @jstangroome and @philipchung.

vllm serve models/gemma-3-27b-it  --enable-auto-tool-choice  --tool-call-parser pythonic --chat-template tool_chat_template_gemma3_pythonic.jinja

FIX #14734

[github-actions]

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[paolovic]

@philipchung please, sign the DCO, e.g., git commit -m "bla" -s

[philipchung]

@paolovic I've signed the DCO now.

[gyin94]

thanks for adding it. but this caused hanging when tool parser failed for some results. especially 4b

[paolovic]

thanks for adding it. but this caused hanging when tool parser failed for some results. especially 4b

Hi,
which precise version of the model and vllm are you using?