List document type codes and the number of documents in each code.
SELECT document_type_code ,  count(*) FROM Documents GROUP BY document_type_code
SELECT document_type_code ,  count(*) FROM Documents GROUP BY document_type_code
[{'Document_Type_Code': 'BK', 'count(*)': 6}, {'Document_Type_Code': 'CV', 'count(*)': 3}, {'Document_Type_Code': 'FM', 'count(*)': 1}, {'Document_Type_Code': 'PP', 'count(*)': 5}]