public function getFieldHistory(string $field) : Collection
    {
        return $this->revisions->map(function ($revision) use ($field) : ?array {
            if ($revision->old($field) == $revision->new($field)) {
                return null;
            }

            return [
                'created_at' => (string) $revision->created_at,
                'user_id' => $revision->executor->id ?? null,
                'user_email' => $revision->executor->email ?? null,
                'old' => $revision->old($field),
                'new' => $revision->new($field),
            ];
        })->filter()->values();
    }