There must be a faster way than simply iterating through all the numbers

Euler Project #1.py

import unittest

def SumMultiplesOfThreeOrFive(number):
    return sum(i for i in range(1,number) if (i % 3 == 0 or i % 5 == 0))
    #for i in range(1,number):
    #    if (i % 3 == 0 or i % 5 == 0):
    #       sum += i
    #return sum

class TestSumMultiplesOfThreeOrFive(unittest.TestCase):
    def test_case(self):
        self.assertEqual(SumMultiplesOfThreeOrFive(10),23)
        
if __name__ == '__main__':
unittest.main(exit=False)