docs: function(key, callback) {
  		if (typeof data[key] == 'undefined') {
  			callback && callback(null, null)
  		} else if (typeof data[key] == 'string' || typeof data[key] == 'number' || typeof data[key] == 'boolean') {
  			callback && callback(null, data[key])
  		} else {
  			callback && callback(typeError('getBytes', 'string or number', key))
  		}
  	}