langchain/experimental/generative_agents/generative_agent.py/GenerativeAgent/_get_entity_from_observation
class GenerativeAgent:    def _get_entity_from_observation(self, observation: str) -> str:
        prompt = PromptTemplate.from_template(
            "What is the observed entity in the following observation? {observation}"
            + "\nEntity="
        )
        return self.chain(prompt).run(observation=observation).strip()