code: def to_csv(self, filepath, sep=',', header=True, index=True):
          
          from ..io import to_csv
  
          return to_csv(self, filepath, sep=sep, header=header, index=index)
docs: Save DataFrame as csv.
  
          Parameters
          ----------
          filepath : str
          sep : str, optional
              Separator used between values.
          header : bool, optional
              Whether to save the header.
          index : bool, optional
              Whether to save the index columns.
  
          Returns
          -------
          None