code: def sub_tag_value(self, path, follow=True):
          
          rec = self.sub_tag(path, follow)
          if rec:
              return rec.value
          return None
docs: Returns value of a direct sub-record or None.
  
          Works as :py:meth:`sub_tag` but returns value of a sub-record
          instead of sub-record itself.
  
          :param str path: tag names separated by slashes.
          :param boolean follow: If True then resolve pointers.
          :return: String or `None` if sub-record with a given
              tag does not exist.