code: def tabs_obsolete(physical_line):
      r
      indent = INDENT_REGEX.match(physical_line).group(1)
      if '\t' in indent:
          return indent.index('\t'), "W191 indentation contains tabs"
docs: r"""For new projects, spaces-only are strongly recommended over tabs.
  
      Okay: if True:\n    return
      W191: if True:\n\treturn