Question: what is the secondary stain in the acid fast stain
[{'answer': "loeffler 's methylene blue", 'provenance': [{'wikipedia_id': '1126212', 'title': 'Ziehl–Neelsen stain', 'start_paragraph_id': 13, 'start_character': 104, 'end_paragraph_id': 13, 'end_character': 129, 'bleu_score': 1.0, 'section': 'Section::::Modifications.\n'}]}]