# File lib/ruote/exp/ro_persist.rb, line 64
    def try_unpersist

      r = @context.storage.delete(@h)

      #t = Thread.current.object_id.to_s[-3..-1]
      #puts "- unp #{h.fei['expid']} #{tree.first} #{h._rev} #{t} -> #{r.class}"
      #Ruote.p_caller('- unp') #if r != nil || h.fei['expid'] == '0_0'

      return r if r

      #if h.has_error
      err = @context.storage.get('errors', "err_#{Ruote.to_storage_id(h.fei)}")
      @context.storage.delete(err) if err
      #end
        # removes any error in the journal for this expression
        # since it will now be gone, no need to keep track of its errors

      nil
    end