docstr: Converts the string to Lower Case.
  
  Returns:
      ret (pd.DataFrame): String converted to Lower Case.
docstr_tok: ["Converts","the","string","to","Lower","Case",".","Returns",":","ret","(","pd.DataFrame",")",":","String","converted","to","Lower","Case","."]
code: def forward(self, df: pd.DataFrame) -> pd.DataFrame:
      """
      Converts the string to Lower Case.
  
      Returns:
          ret (pd.DataFrame): String converted to Lower Case.
      """
  
      ret = pd.DataFrame()
      ret["output"] = df.map(
          lambda s: s.lower() if type(s) is str else s
      )
      return ret
  
imports: import pandas
  from evadb.functions.abstract.abstract_function import AbstractFunction
label_desc: Use image node_id 3 for calling the Lower obj's underlying member method code with example usage: obj.forward(df) and returns: ret