class RubyXL::WorkbookRoot

def stream
  stream = Zip::OutputStream.write_buffer { |zipstream|
    self.rels_hash = {}
    self.relationship_container.owner = self
    collect_related_objects.compact.each { |obj|
      puts "<-- DEBUG: adding relationship to #{obj.class}" if @@debug
      obj.root = self if obj.respond_to?(:root=)
      self.rels_hash[obj.class] ||= []
      self.rels_hash[obj.class] << obj
    }
    self.rels_hash.keys.sort_by{ |c| c::SAVE_ORDER }.each { |klass|
      puts "<-- DEBUG: saving related #{klass} files" if @@debug
      self.rels_hash[klass].select! { |obj|
        puts "<-- DEBUG:   > #{obj.xlsx_path}" if @@debug
        obj.add_to_zip(zipstream)
      }
    }
  }
  stream.rewind
  stream
end