# File lib/ruote/exp/fe_add_branches.rb, line 111
    def find_concurrent_iterator

      #
      # ref ?

      if ref = attribute(:ref)

        return lookup_variable(ref)
      end

      #
      # no :ref, lookup first parent that is a concurrent_iterator

      exp = self.parent

      loop do

        break if exp.nil?
        break if exp.is_a?(ConcurrentIteratorExpression)

        exp = exp.parent
      end

      exp ? exp.h.fei : nil
    end