public function check(): bool
    {
        return $this->installable = $this->items->filter(function ($specification) {
            return $specification->check() === false && $specification->optional() === false;
        })->isEmpty();
    }
public function check(): bool
    {
        return $this->installable = $this->items->filter(function ($specification) {
            return $specification->check() === false && $specification->optional() === false;
        })->isEmpty();
    }
public function check ( ) : bool { return $ this -> installable = $ this -> items -> filter ( function ( $ specification ) { return $ specification -> check ( ) === false && $ specification -> optional ( ) === false ; } ) -> isEmpty ( ) ; }
Check all requirement.

@return bool
Check all requirement .