def filter(context, nodelist, filter_exp):
output = nodelist.render(context)<EOL>context.update({'<STR_LIT>': output})<EOL>filtered = filter_expr.resolve(context)<EOL>context.pop()<EOL>return filtered<EOL>
Filters the contents of the block through variable filters.

Filters can also be piped through each other, and they can have
arguments -- just like in variable syntax.

Sample usage::

    {% filter force_escape|lower %}
        This text will be HTML-escaped, and will appear in lowercase.
    {% endfilter %}