public function dateToString($format, $expression) : self
    {
        $this->expr->dateToString($format, $expression);

        return $this;
    }
public function dateToString($format, $expression) : self
    {
        $this->expr->dateToString($format, $expression);

        return $this;
    }
public function dateToString ( $ format , $ expression ) : self { $ this -> expr -> dateToString ( $ format , $ expression ) ; return $ this ; }
Converts a date object to a string according to a user-specified format.

The format string can be any string literal, containing 0 or more format
specifiers.
The date argument can be any expression as long as it resolves to a date.

@see http://docs.mongodb.org/manual/reference/operator/aggregation/dateToString/
@see Expr::dateToString

@param string     $format
@param mixed|Expr $expression
Converts a date object to a string according to a user - specified format .