class_docstr: Unit tests for Agent class
code: def llm(self, output: Optional[str] = None) -> FakeLLM:
      return FakeLLM(output=output)
  
imports: from typing import Optional
  from unittest.mock import Mock
  from pandasai.agent import Agent
  import pandas
  import pytest
  from pandasai.llm.fake import FakeLLM
  from pandasai.prompts.clarification_questions_prompt import ClarificationQuestionPrompt
  from pandasai.prompts.explain_prompt import ExplainPrompt
  from pandasai.smart_datalake import SmartDatalake
label_desc: Use image node_id 2 for calling the TestAgent obj's underlying member method code with example usage: obj.llm(output) and returns: FakeLLM