Question: what do brackets in an chemical equation mean
[{'answer': 'chemical molecular formula', 'provenance': [{'wikipedia_id': '33034771', 'title': 'Defining equation (physical chemistry)', 'start_paragraph_id': 6, 'start_character': 90, 'end_paragraph_id': 6, 'end_character': 116, 'bleu_score': 1.0, 'section': 'Section::::Notes on nomenclature.\n'}]}, {'provenance': [{'wikipedia_id': '33034771', 'title': 'Defining equation (physical chemistry)', 'start_paragraph_id': 6, 'start_character': 0, 'end_paragraph_id': 6, 'end_character': 229, 'bleu_score': 0.8749766281017171, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 18271408961522367814}, 'section': 'Section::::Notes on nomenclature.\n'}]}]