public function hasTerm($term_id) {
    $term = ($term_id instanceof Term) ? $term_id : Term::findOrFail($term_id);

    $term_relation = [
      'term_id' => $term->id,
      'vocabulary_id' => $term->vocabulary_id,
    ];

    return ($this->related()->where('term_id', $term_id)->count()) ? TRUE : FALSE;
  }