Optional. A set of function names that, when provided, limits the functions the model
will call. This should only be set when the Mode is ANY. Function names should match
[FunctionDeclaration.name]. With mode set to ANY, model will predict a function call
from the set of function names provided.
mode
Optional. Specifies the mode in which function calling should execute. If unspecified,
the default value will be set to AUTO.