'convert all values in table to a list of lists of strings'

def str_vals(self):

    self._set_fill_values(self.cols)
    self._set_col_formats()
    for col in self.cols:
        col.str_vals = list(col.info.iter_str_vals())
    self._replace_vals(self.cols)
    return [col.str_vals for col in self.cols]
