code: function (name, validation) {
  		if (name == null && validation == null) {
  			delete this.isRequired;
  			return this;
  		}
  
  		return this.field(name).validate(validation);
  	}
docs: add new required nested schema by construct
  
  @method
  @this {Schema}
  @param {?String} [name] - field name.
  @param {?*} [validation] - validation options.
  @returns {Schema}