input: Write a function to find prime factors of a given number.
  assert find_prime_factors(10) == [2, 5]
  assert find_prime_factors(30) == [2, 3, 5]
  assert find_prime_factors(100) == [2, 2, 5, 5]
  assert find_prime_factors(13) == [13]
output: def find_prime_factors(n):
      factors = []
      divisor = 2
      while n > 1:
          while n % divisor == 0:
              factors.append(divisor)
              n //= divisor
          divisor += 1
      return factors