'sum of elements matrix[(row1,col1)..(row2,col2)], inclusive.
:type row1: int
:type col1: int
:type row2: int
:type col2: int
:rtype: int'

def sumRegion(self, row1, col1, row2, col2):

    return (((self.__sum(row2, col2) - self.__sum(row2, (col1 - 1))) - self.__sum((row1 - 1), col2)) + self.__sum((row1 - 1), (col1 - 1)))
