Liquid assign_to

Hello using liquid markup i am trying to do the following.

{{ 'holiday' | album_thumbs | assign_to 'asset_list' }}

{% for asset in asset_list %}
   "link: " + {{ asset | asset_path }}
{% endfor %}

It should return a list with all assets for the loop, but the asset_list
variable never gets set. It just returns #### (number of records) on
this line:

{{ 'holiday' | album_thumbs | assign_to 'asset_list' }}

I have created the following function inside a (drop) filter

  def album_thumbs(tag)
      @context['domain'].find_assets_tagged_with(tag)
  end

I am using Liquid 1.9.0 on rails 2.2.2