Question: 
Write a function to sum a specific column of a list in a given list of lists.


Model's Code:
def sum_column(matrix, column_index):
    return sum(row[column_index] for row in matrix)



Sample Correct Code:
def sum_column(list1, C):
    result = sum(row[C] for row in list1)
    return result


Asserts:
assert sum_column( [[1,2,3,2],[4,5,6,2],[7,8,9,5],],0)==12
assert sum_column( [[1,2,3,2],[4,5,6,2],[7,8,9,5],],1)==15
assert sum_column( [[1,2,3,2],[4,5,6,2],[7,8,9,5],],3)==9


Tests:
Test 1 of 3: PASS
Test 2 of 3: PASS
Test 3 of 3: PASS

Test 827 of 974: 633/827 (76.54171704957679%): success