def get_config_update(self, name: str, arg: Expression, lax_extra: bool = False) -> ModelConfigData | None:
        """Determines the config update due to a single kwarg in the ConfigDict definition.

        Warns if a tracked config attribute is set to a value the plugin doesn't know how to interpret (e.g., an int)
        """
        if name not in self.tracked_config_fields:
            return None
        if name == 'extra':
            if isinstance(arg, StrExpr):
                forbid_extra = arg.value == 'forbid'
            elif isinstance(arg, MemberExpr):
                forbid_extra = arg.name == 'forbid'
            else:
                if not lax_extra:
                    # Only emit an error for other types of `arg` (e.g., `NameExpr`, `ConditionalExpr`, etc.) when
                    # reading from a config class, etc. If a ConfigDict is used, then we don't want to emit an error
                    # because you'll get type checking from the ConfigDict itself.
                    #
                    # It would be nice if we could introspect the types better otherwise, but I don't know what the API
                    # is to evaluate an expr into its type and then check if that type is compatible with the expected
                    # type. Note that you can still get proper type checking via: `model_config = ConfigDict(...)`, just
                    # if you don't use an explicit string, the plugin won't be able to infer whether extra is forbidden.
                    error_invalid_config_value(name, self._api, arg)
                return None
            return ModelConfigData(forbid_extra=forbid_extra)
        if name == 'alias_generator':
            has_alias_generator = True
            if isinstance(arg, NameExpr) and arg.fullname == 'builtins.None':
                has_alias_generator = False
            return ModelConfigData(has_alias_generator=has_alias_generator)
        if isinstance(arg, NameExpr) and arg.fullname in ('builtins.True', 'builtins.False'):
            return ModelConfigData(**{name: arg.fullname == 'builtins.True'})
        error_invalid_config_value(name, self._api, arg)
        return None
Determines the config update due to a single kwarg in the ConfigDict definition.

        Warns if a tracked config attribute is set to a value the plugin doesn't know how to interpret (e.g., an int)
        
pydantic/mypy.py