code: function fetchDocs (docNames, qs0, callback0) {
        const { opts, callback } = getCallback(qs0, callback0)
        opts['include_docs'] = true
  
        return relax({
          db: dbName,
          path: '_all_docs',
          method: 'POST',
          qs: opts,
          body: docNames
        }, callback)
      }
docs: http://docs.couchdb.org/en/latest/api/database/bulk-api.html#post--db-_all_docs