Returns all top-level facets. The returned values depend on the given type:
            Concept or All (Concepts and Collections). Default All is used.

        :param (str) type: Concepts or All (Concepts and Collections) top facets to return
        :return: A :class:`lst` of concepts (and collections).

def _get_top(self, type='All', **kwargs):
        """ Returns all top-level facets. The returned values depend on the given type:
            Concept or All (Concepts and Collections). Default All is used.

        :param (str) type: Concepts or All (Concepts and Collections) top facets to return
        :return: A :class:`lst` of concepts (and collections).
        """

        if type == "concepts" :
            type_values = "(?Type = skos:Concept)"
        else:
            type_values = "((?Type = skos:Concept) || (?Type = skos:Collection))"

        query = """SELECT ?Subject ?Id ?Type ?Term (lang(?Term) as ?Lang)
                {
                ?Subject a gvp:Facet; rdf:type ?Type;
                 dc:identifier ?Id; skos:inScheme %s:;.
                 OPTIONAL {
                  {?Subject xl:prefLabel [skosxl:literalForm ?Term]}
                          }
                FILTER (%s)
                }""" % (self.vocab_id, type_values)
        ret= self._get_answer(query, **kwargs)
        language = self._get_language(**kwargs)
        sort = self._get_sort(**kwargs)
        sort_order = self._get_sort_order(**kwargs)
        return self._sort(ret, sort, language, sort_order == 'desc')