Is "SendMessageToUser" class necessary in pydantic-models-to-grammar-examples.py?

[bartmch]

When using the example in "pydantic-models-to-grammar-examples.py" for the calculator you pass the pydantic classes [SendMessageToUser, Calculator] to generate_gbnf_grammar_and_documentation in order to create the gbnf and the doc which are then passed on to the LLM. During and after processing a prompt, only the class Calculator seems to be used. Why and where are you actually using SendMessageToUser.