def _deserialize(data)
      @data = {}
      data.each { |k, v| @data[k] = v.is_a?(POReference) ?
                                    POXReference.new(@store, v.id) : v }
      @data
    end
def _deserialize(data)
      @data = {}
      data.each { |k, v| @data[k] = v.is_a?(POReference) ?
                                    POXReference.new(@store, v.id) : v }
      @data
    end
Restore the persistent data from a single data structure.
 This is a library internal method. Do not use outside of this library.
 @param data [Hash] the actual Hash object
 @private