[{'avg': 200, 'dept': '001', 'qty': 200, 'sku': 'bar'}, {'avg': 200, 'dept':
    '001', 'qty': 400, 'sku': 'foo'}, {'avg': 450, 'dept': '002', 'qty': 
    900, 'sku': 'baz'}, {'avg': 600, 'dept': '002', 'qty': 600, 'sku':
    'qux'}, {'avg': 700, 'dept': '003', 'qty': 700, 'sku': 'foo'}]
Group by multiple keys and summarize/average values of a list of dictionaries