code: def update_spec(self):
          
  
          if self.datafile.exists:
              with self.datafile.reader as r:
  
                  self.header_lines = r.info['header_rows']
                  self.comment_lines = r.info['comment_rows']
                  self.start_line = r.info['data_start_row']
                  self.end_line = r.info['data_end_row']
docs: Update the source specification with information from the row intuiter, but only if the spec values
          are not already set.