code: def _mark_quoted_email_splitlines(markers, lines):
      
      # Create a list of markers to easily alter specific characters
      markerlist = list(markers)
      for i, line in enumerate(lines):
          if markerlist[i] != 'm':
              continue
          for pattern in SPLITTER_PATTERNS:
              matcher = re.search(pattern, line)
              if matcher:
                  markerlist[i] = 's'
                  break
  
      return "".join(markerlist)
docs: When there are headers indented with '>' characters, this method will
      attempt to identify if the header is a splitline header. If it is, then we
      mark it with 's' instead of leaving it as 'm' and return the new markers.