docs: def _magickfy_topics(topics):
          """Add the magick to the topics if missing.
          """
          # If topic does not start with messages._MAGICK (pytroll:/), it will be
          # prepended.
          if topics is None:
              return None
          if isinstance(topics, six.string_types):
              topics = [topics, ]
          ts_ = []
          for t__ in topics:
              if not t__.startswith(_MAGICK):
                  if t__ and t__[0] == '/':
                      t__ = _MAGICK + t__
                  else:
                      t__ = _MAGICK + '/' + t__
              ts_.append(t__)
          return ts_