Question: when was the construction of the berlin wall finished
[{'answer': 'about 1980', 'provenance': [{'wikipedia_id': '3722', 'title': 'Berlin Wall', 'start_paragraph_id': 58, 'start_character': 174, 'end_paragraph_id': 58, 'end_character': 184, 'bleu_score': 1.0, 'section': 'Section::::Structure and adjacent areas.:Layout and modifications.\n'}]}, {'provenance': [{'wikipedia_id': '3722', 'title': 'Berlin Wall', 'start_paragraph_id': 58, 'start_character': 0, 'end_paragraph_id': 58, 'end_character': 632, 'bleu_score': 0.8159083017424821, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7891873045924539279}, 'section': 'Section::::Structure and adjacent areas.:Layout and modifications.\n'}]}]