docs: function save_result_to(self) {
  	if( is.obj(self) && is.func(self.nopg) ) {
  		return function(doc) { return self.update(doc); };
  	}
  
  	if( is.obj(self) && is.array(self._values) ) {
  		return function(doc) {
  			self._values.push( doc );
  			return self;
  		};
  	}
  
  	throw new TypeError("Unknown target: " + (typeof self));
  }