code: def update_line(self, section, old_line, new_line, once=False):
          
          try:
              s = self._get_section(section, create=False)
          except KeyError:
              return 0
          return s.update(old_line, new_line, once=once)
docs: Replace all lines matching `old_line` with `new_line`.
  
          If ``once`` is set to True, remove only the first instance.
  
          Returns:
              int: the number of updates performed