static const gchar *
get_license (ChamplainMapSource *map_source)
{
  ChamplainMapSourceChain *source_chain = CHAMPLAIN_MAP_SOURCE_CHAIN (map_source);
  g_return_val_if_fail (source_chain, NULL);

  ChamplainMapSourceChainPrivate *priv = source_chain->priv;
  g_return_val_if_fail (priv->stack_top, NULL);

  return champlain_map_source_get_license (priv->stack_top);
}
static const gchar *
get_license (ChamplainMapSource *map_source)
{
  g_return_val_if_fail (CHAMPLAIN_IS_TILE_CACHE (map_source), NULL);

  ChamplainMapSource *next_source = champlain_map_source_get_next_source (map_source);

  g_return_val_if_fail (CHAMPLAIN_IS_MAP_SOURCE (next_source), NULL);

  return champlain_map_source_get_license (next_source);
}