langchain/prompts/few_shot_with_templates.py/FewShotPromptWithTemplates/template_is_valid
class FewShotPromptWithTemplates:    def template_is_valid(cls, values: Dict) -> Dict:
        """Check that prefix, suffix and input variables are consistent."""
        if values["validate_template"]:
            input_variables = values["input_variables"]
            expected_input_variables = set(values["suffix"].input_variables)
            expected_input_variables |= set(values["partial_variables"])
            if values["prefix"] is not None:
                expected_input_variables |= set(values["prefix"].input_variables)
            missing_vars = expected_input_variables.difference(input_variables)
            if missing_vars:
                raise ValueError(
                    f"Got input_variables={input_variables}, but based on "
                    f"prefix/suffix expected {expected_input_variables}"
                )
        return values