code: def df64bitto32bit(tbl):
      
      newtbl = pd.DataFrame(index=tbl.index)
      for colname in tbl.columns:
          newtbl[colname] = series64bitto32bit(tbl[colname])
      return newtbl
docs: Convert a Pandas dataframe from 64 bit types to 32 bit types to save
      memory or disk space.
  
      Parameters
      ----------
      tbl : The dataframe to convert
  
      Returns
      -------
      The converted dataframe