public function setUnion($expression1, $expression2, ...$expressions) : self
    {
        $this->expr->setUnion(...func_get_args());

        return $this;
    }
public function setUnion($expression1, $expression2, ...$expressions) : self
    {
        $this->expr->setUnion(...func_get_args());

        return $this;
    }
public function setUnion ( $ expression1 , $ expression2 , ... $ expressions ) : self { $ this -> expr -> setUnion ( ... func_get_args ( ) ) ; return $ this ; }
Takes two or more arrays and returns an array containing the elements
that appear in any input array.

The arguments can be any valid expression as long as they each resolve to an array.

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

@param mixed|Expr $expression1
@param mixed|Expr $expression2
@param mixed|Expr ...$expressions Additional sets
Takes two or more arrays and returns an array containing the elements that appear in any input array .