# File lib/ruote/exp/fe_filter.rb, line 623
    def referenced_filter

      prefix, key = attribute_text.split(':')

      return nil unless %w[ v var variable f field ].include?(prefix)

      filter = prefix.match(/^v/) ?
        lookup_variable(key) : Ruote.lookup(h.applied_workitem['fields'], key)

      if filter.is_a?(Hash) and i = filter['in']
        return i
      end

      filter
    end