public function remove(string $entryIdentifier): bool
    {
        if (!isset($this->entries[$entryIdentifier])) {
            return false;
        }
        unset($this->entries[$entryIdentifier]);
        foreach (array_keys($this->tagsAndEntries) as $tag) {
            if (isset($this->tagsAndEntries[$tag][$entryIdentifier])) {
                unset($this->tagsAndEntries[$tag][$entryIdentifier]);
            }
        }
        return true;
    }