'array', 'meta' => 'array', 'order' => 'integer', 'order_index' => 'integer', 'created_at' => 'datetime', 'updated_at' => 'datetime', ]; public function file(): BelongsTo { return $this->belongsTo(SourceFile::class, 'source_file_id'); } public function parts(): HasMany { return $this->hasMany(PaperPart::class, 'source_paper_id'); } public function textbook(): BelongsTo { return $this->belongsTo(Textbook::class, 'textbook_id'); } public function questions(): HasMany { return $this->hasMany(Question::class, 'source_paper_id'); } public function candidates(): HasMany { return $this->hasMany(PreQuestionCandidate::class, 'source_paper_id'); } public function questionRefs(): HasMany { return $this->hasMany(PaperQuestionRef::class, 'source_paper_id'); } public function series(): BelongsTo { return $this->belongsTo(TextbookSeries::class, 'series_id'); } }