code: function add_shared(hash, customTags, doc_map) {
      hash = utils.merge(hash, {
        "inheritable" : !!doc_map["inheritable"],
        "inheritdoc" : extract(doc_map, "inheritdoc"),
        "related" : extract(doc_map, "related"),
        "see" : extract(doc_map, "see"),
        "private" : extract(doc_map, "private") !== null ? true : false,
        "experimental" : extract(doc_map, "experimental") !== null ? true : false,
        "ignore" : extract(doc_map, "ignore") !== null ? true : false,
        "author" : extract_plural(doc_map["author"] || []),
        "version" : extract(doc_map, "version"),
        "since" : extract(doc_map, "since"),
        "todo" : extract(doc_map, "todo")
      });
  
      if (customTags !== undefined) {
        var custom = {};
        _.each(customTags, function(tag) {
          var text = extract(doc_map, tag);
          if (text !== null) {
            custom[tag] = text.doc.length > 0 ? text.doc : true;
          }
        });
  
        hash = utils.merge(hash, custom);
      }
  
      return hash;
  }
docs: Detects properties common for each doc-object and adds them