-- | Gets all namespaces directly referred by a NsItem
referredNss :: NsItem -- ^ The name to get all directly
                      --   referred namespaces for
            -> S.Set NsName
referredNss (_, Nothing, _) = S.empty
referredNss :: NsItem -- ^ The name to get all directly
                      --   referred namespaces for
            -> S.Set NsName
referredNss (_, Nothing, _) = S.empty
referredNss (_, Nothing, _) = S.empty