code: public function valuesExp($expression, $bind = false)
  	{
  		return $this->appendPart(
  			CmdInsert::PART_VALUES, 
  			$expression,
  			$bind
  		);
  	}
docs: Insert data using given expression. That can be sued if some of the values are expressions.
  Expressions must be Sql safe.
  @param string $expression Expression to insert. Expression must start from ( and end with ).
  Expression can contain a number of rows to insert. It will not be validated in no way so number
  of fields must match number of table fields.
  @param mixed|array $bind Single bind param or array of bind params.
  @return static