The flush tag tells Twig to flush the output buffer:
{% flush %}
Note
Internally, Twig uses the PHP flush function.
© 2009–2017 by the Twig Team
Licensed under the three clause BSD license.
The Twig logo is © 2010–2017 SensioLabs
https://twig.sensiolabs.org/doc/2.x/tags/flush.html