docs: def sub_tag(self, path, follow=True):
          """Returns direct sub-record with given tag name or None.
  
          Path can be a simple tag name, in which case the first direct
          sub-record of this record with the matching tag is returned. Path
          can also consist of several tags separated by slashes, in that case
          sub-records are searched recursively.
  
          If `follow` is True then pointer records are resolved and pointed
          record is used instead of pointer record, this also works for all
          intermediate records in a path.
  
          :param str path: tag names separated by slashes.
          :param boolean follow: If True then resolve pointers.
          :return: `Record` instance or `None` if sub-record with a given
              tag does not exist.
          """
          tags = path.split('/')
          rec = self
          for tag in tags:
              recs = [x for x in (rec.sub_records or []) if x.tag == tag]
              if not recs:
                  return None
              rec = recs[0]
              if follow and isinstance(rec, Pointer):
                  rec = rec.ref
          return rec