docstr: List the index of the DataFrames that are needed to execute the code. The goal
  is to avoid to run the connectors if the code does not need them.
  
  Args:
      code (str): Python code to execute
  
  Returns:
      List[int]: A list of the index of the DataFrames that are needed to execute
      the code.
docstr_tok: ["List","the","index","of","the","DataFrames","that","are","needed","to","execute","the","code",".","The","goal","is","to","avoid","to","run","the","connectors","if","the","code","does","not","need","them",".","Args",":","code","(","str",")",":","Python","code","to","execute","Returns",":","List","[","int","]",":","A","list","of","the","index","of","the","DataFrames","that","are","needed","to","execute","the","code","."]
code: def _required_dfs(self, code: str) -> List[str]:
      """
      List the index of the DataFrames that are needed to execute the code. The goal
      is to avoid to run the connectors if the code does not need them.
  
      Args:
          code (str): Python code to execute
  
      Returns:
          List[int]: A list of the index of the DataFrames that are needed to execute
          the code.
      """
  
      # Sometimes GPT-3.5/4 use a for loop to iterate over the dfs (even if there is only one)
      # or they concatenate the dfs. In this case we need all the dfs
      if "for df in dfs" in code or "pd.concat(dfs)" in code:
          return self._dfs
  
      required_dfs = []
      for i, df in enumerate(self._dfs):
          if f"dfs[{i}]" in code:
              required_dfs.append(df)
          else:
              required_dfs.append(None)
      return required_dfs
  
imports: import re
  import ast
  import uuid
  from collections import defaultdict
  import astor
  import pandas
  from pandasai.helpers.path import find_project_root
  from pandasai.helpers.skills_manager import SkillsManager
  from pandasai.helpers.sql import extract_table_names
  from .node_visitors import AssignmentVisitor, CallVisitor
  from .save_chart import add_save_chart
  from .optional import import_dependency
  from ..exceptions import BadImportError, MaliciousQueryError, NoResultFoundError, InvalidConfigError
  from ..constants import WHITELISTED_BUILTINS, WHITELISTED_LIBRARIES
  from typing import Union, List, Generator, Any
  from ..helpers.logger import Logger
  from ..schemas.df_config import Config
  import logging
  import traceback
label_desc: Use image node_id 2 for calling the CodeManager obj's underlying member method code with example usage: obj._required_dfs(code) and returns: required_dfs, self