def find_filter(self, filter_name):
        if filter_name in self.filters:
            return self.filters[filter_name]
        else:
            raise TemplateSyntaxError("Invalid filter: '%s'" % filter_name)
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.3/django/template/base.py/Parser.find_filter/original