'array', 'order' => 'integer', 'created_at' => 'datetime', 'updated_at' => 'datetime', ]; public function paper(): BelongsTo { return $this->belongsTo(SourcePaper::class, 'source_paper_id'); } public function part(): BelongsTo { return $this->belongsTo(PaperPart::class, 'part_id'); } public function candidate(): BelongsTo { return $this->belongsTo(PreQuestionCandidate::class, 'candidate_id'); } }