langchain/prompts/example_selector/length_based.py/LengthBasedExampleSelector/add_example
class LengthBasedExampleSelector:    def add_example(self, example: Dict[str, str]) -> None:
        """Add new example to list."""
        self.examples.append(example)
        string_example = self.example_prompt.format(**example)
        self.example_text_lengths.append(self.get_text_length(string_example))