Question: in ramayana who is the father of ravana
[{'answer': 'Vishrava', 'provenance': [{'wikipedia_id': '100234', 'title': 'Ravana', 'start_paragraph_id': 5, 'start_character': 263, 'end_paragraph_id': 5, 'end_character': 271, 'bleu_score': 1.0, 'section': 'Section::::Etymology.\n'}]}]