Get items from feed cache while trying to emulate
        how API handles offset/since/before parameters

def get_cached(self):
        """ Get items from feed cache while trying to emulate
        how API handles offset/since/before parameters
        """
        def id_in_list(list, id):
            if id:
                if [i for i in list if i.id == id]:
                    return True
                else:
                    raise PyPumpException("id %r not in feed." % self._since)

        tmp = []
        if self._before is not None:
            # return list based on before param
            if not id_in_list(self.feed._items, self._before):
                return tmp
            if isinstance(self._before, six.string_types):
                found = False
                for i in self.feed._items:
                    if not found:
                        if i.id == self._before:
                            found = True
                        continue
                    else:
                        tmp.append(i)
                self._before = False
            return tmp

        if self._since is not None:
            # return list based on since param
            if not id_in_list(self.feed._items, self._since):
                return tmp
            if isinstance(self._since, six.string_types):
                found = False
                for i in self.feed._items:
                    if i.id == self._since:
                        found = True
                        break
                    else:
                        tmp.append(i)
                self._since = False
            return reversed(tmp)

        if not hasattr(self, 'usedcache'):
            self.usedcache = True  # invalidate cache

            if isinstance(self._offset, int):
                # return list based on offset
                return self.feed._items[self._offset:]

            return self.feed._items
        else:
            return tmp