code: function (type) {
      var meta = findMeta(type);
      var set = joi.array().sparse(false).unique().items(type);
      return joi.alternatives().meta({
        cql: true,
        type: 'set',
        setType: meta.type,
        serialize: convertArray(meta.serialize),
        deserialize: convertArray(meta.deserialize)
      }).try(set, joi.object().keys({
        add: set,
        remove: set
      }).or('add', 'remove').unknown(false));
    }
docs: Create a joi object that can validate a `set` for Cassandra.
  
  @param {Joi} type - used for validating the values of the set
  @returns {Joi} - the validator