# File lib/asciidoctor/converter/docbook5.rb, line 304
    def open node
      case node.style
      when 'abstract'
        if node.parent == node.document && node.document.doctype == 'book'
          warn 'asciidoctor: WARNING: abstract block cannot be used in a document without a title when doctype is book. Excluding block content.'
          ''
        else
          %(<abstract>
#{title_tag node}#{resolve_content node}
</abstract>)
        end
      when 'partintro'
        unless node.level == 0 && node.parent.context == :section && node.document.doctype == 'book'
          warn 'asciidoctor: ERROR: partintro block can only be used when doctype is book and it\'s a child of a part section. Excluding block content.'
          ''
        else
          %(<partintro#{common_attributes node.id, node.role, node.reftext}>
#{title_tag node}#{resolve_content node}
</partintro>)
        end
      else
        node.content
      end
    end