public function not($expression) : self
    {
        return $this->operator('$not', $expression instanceof Expr ? $expression->getQuery() : $expression);
    }
public function not($expression) : self
    {
        return $this->operator('$not', $expression instanceof Expr ? $expression->getQuery() : $expression);
    }
public function not ( $ expression ) : self { return $ this -> operator ( '$not' , $ expression instanceof Expr ? $ expression -> getQuery ( ) : $ expression ) ; }
Negates an expression for the current field.

@see Builder::not()
@see http://docs.mongodb.org/manual/reference/operator/not/

@param array|Expr $expression
Negates an expression for the current field .