@backtrader it seems that doesn't work now. Custom filter should be added after Resampler filter which always return True.
From the sources of feed.py:

        for ff, fargs, fkwargs in self._filters:
            # previous filter may have put things onto the stack
            if self._barstack:
                for i in range(len(self._barstack)):
                    self._fromstack(forward=True)
                    retff = ff(self, *fargs, **fkwargs)
            else:
                retff = ff(self, *fargs, **fkwargs)

            if retff:  # bar removed from systemn
                break  # out of the inner loop

And that means that no filters will be executed after Resampler.
So, what is the right way to resample custom lines?
Thanks.