code: function (name, args) {
              args = argsToArray(arguments).slice(1);
              var block = isFunction(args[args.length - 1]) ? args.pop : null;
              this.constraints.push({name:name, type:"check", check:block || args});
          }
docs: Adds a named constraint (or unnamed if name is nil) to the DDL,
  with the given block or args.
  @example
  DB.createTable("test", function(){
  this.constraint("blah", {num : {between : [1,5]}})
  //=> CONSTRAINT blah CHECK num >= 1 AND num <= 5
  this.check("foo", function(){
  return this.num.gt(5);
  }); # CONSTRAINT foo CHECK num > 5
  });
  @param {String|patio.sql.Identifier} name the name of the constraint
  @param {...} args variable number of arguments to create the constraint filter.
  See {@link patio.Dataset#filter} for valid filter arguments.