code: def fetch(self, recursive=1, fields=None, detail=None,
                filters=None, parent_uuid=None, back_refs_uuid=None):
          
  
          params = self._format_fetch_params(fields=fields, detail=detail, filters=filters,
                                             parent_uuid=parent_uuid, back_refs_uuid=back_refs_uuid)
          data = self.session.get_json(self.href, **params)
  
          if not self.type:
              self.data = [Collection(col["link"]["name"],
                                      fetch=recursive - 1 > 0,
                                      recursive=recursive - 1,
                                      fields=self._fetch_fields(fields),
                                      detail=detail or self.detail,
                                      filters=self._fetch_filters(filters),
                                      parent_uuid=self._fetch_parent_uuid(parent_uuid),
                                      back_refs_uuid=self._fetch_back_refs_uuid(back_refs_uuid))
                           for col in data['links']
                           if col["link"]["rel"] == "collection"]
          else:
              # when detail=False, res == {resource_attrs}
              # when detail=True, res == {'type': {resource_attrs}}
              self.data = [Resource(self.type,
                                    fetch=recursive - 1 > 0,
                                    recursive=recursive - 1,
                                    **res.get(self.type, res))
                           for res_type, res_list in data.items()
                           for res in res_list]
  
          return self
docs: Fetch collection from API server
  
          :param recursive: level of recursion
          :type recursive: int
          :param fields: fetch only listed fields.
                         contrail 3.0 required
          :type fields: [str]
          :param detail: fetch all fields
          :type detail: bool
          :param filters: list of filters
          :type filters: [(name, value), ...]
          :param parent_uuid: filter by parent_uuid
          :type parent_uuid: v4UUID str or list of v4UUID str
          :param back_refs_uuid: filter by back_refs_uuid
          :type back_refs_uuid: v4UUID str or list of v4UUID str
  
          :rtype: Collection