def imap_unordered_async(self, func, iterable, chunksize=None, callback=None):
        """A variant of the imap_unordered() method which returns an
        ApplyResult object that provides an iterator (next
        method(timeout) available).

        If callback is specified then it should be a callable which
        accepts a single argument. When the resulting iterator becomes
        ready, callback is applied to it (unless the call
        failed). callback should complete immediately since otherwise
        the thread which handles the results will get blocked."""
        apply_result = ApplyResult(callback=callback)
        collector = UnorderedResultCollector(apply_result)
        self._create_sequences(func, iterable, chunksize, collector)
        return apply_result
A variant of the imap_unordered() method which returns an
        ApplyResult object that provides an iterator (next
        method(timeout) available).

        If callback is specified then it should be a callable which
        accepts a single argument. When the resulting iterator becomes
        ready, callback is applied to it (unless the call
        failed). callback should complete immediately since otherwise
        the thread which handles the results will get blocked.