code: def _preprocess_sgm(line, is_sgm):
    
    if not is_sgm:
      return line
    # In SGM files, remove <srcset ...>, <p>, <doc ...> lines.
    if line.startswith("<srcset") or line.startswith("</srcset"):
      return ""
    if line.startswith("<doc") or line.startswith("</doc"):
      return ""
    if line.startswith("<p>") or line.startswith("</p>"):
      return ""
    # Strip <seg> tags.
    line = line.strip()
    if line.startswith("<seg") and line.endswith("</seg>"):
      i = line.index(">")
      return line[i + 1:-6]
docs: Preprocessing to strip tags in SGM files.