code: function (options, callback) {
    var deleteOps = []
    options.indexes.createKeyStream({gte: '0', lte: '￮'})
      .on('data', function (data) {
        deleteOps.push({type: 'del', key: data})
      })
      .on('error', function (err) {
        options.log.error(err, ' failed to empty index')
        return callback(err)
      })
      .on('end', function () {
        options.indexes.batch(deleteOps, callback)
      })
  }
docs: Remove all keys in DB