When trying to edit a variant, I received the exception:

An exception has been thrown during the rendering of a template in     
SyliusWebBundle:Backend/ProductVariant:_form.html.twig at line 40.

The filter "sylius_90x60" is used but doesn't seem to be defined anywhere. I added a definition for it myself in my config.yml file for the liip_imagine config block, which got rid of the exception, but if this filter is used, it should have its definition somewhere. Am I missing where the definition resides?