Question: what is the function of the pericardial sac
[{'answer': 'Lubricates the heart', 'provenance': [{'wikipedia_id': '244944', 'title': 'Pericardium', 'start_paragraph_id': 22, 'start_character': 12, 'end_paragraph_id': 22, 'end_character': 32, 'bleu_score': 1.0, 'section': 'Section::::Function.\n'}]}, {'answer': 'Sets heart in mediastinum and limits its motion'}, {'answer': 'Prevents excessive dilation of the heart in cases of acute volume overload'}, {'answer': 'Protects it from infections coming from other organs ( such as lungs )'}, {'provenance': [{'wikipedia_id': '244944', 'title': 'Pericardium', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 0, 'bleu_score': 1.0, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5067352834475800613}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '244944', 'title': 'Pericardium', 'section': 'Section::::Function.\n', 'start_paragraph_id': 22, 'end_paragraph_id': 22, 'meta': {'evidence_span': ['Lubricates the heart', 'Lubricates the heart', 'BULLET::::- Lubricates the heart']}}]}, {'provenance': [{'wikipedia_id': '244944', 'title': 'Pericardium', 'section': 'Section::::Abstract.', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 235, 'bleu_score': 0.552841484867401}]}]