docs: def get_patches_ignore_regex(self):
          """Returns a string representing a regex for filtering out patches
  
          This string is parsed from a comment in the specfile that contains the
          word filter-out followed by an equal sign.
  
          For example, a comment as such:
              # patches_ignore=(regex)
  
          would mean this method returns the string '(regex)'
  
          Only a very limited subset of characters are accepted so no fancy stuff
          like matching groups etc.
          """
          match = re.search(r'# *patches_ignore=([\w *.+?[\]|{,}\-_]+)',
                            self.txt)
          if not match:
              return None
          regex_string = match.group(1)
          try:
              return re.compile(regex_string)
          except Exception:
              return None