input: Write a function to get factors of a number in pairs.
  assert get_factors(45)==[[1, 45], [3, 15], [5, 9], [9, 5], [15, 3], [45, 1]]
  assert get_factors(12)==[[1, 12], [2, 6], [3, 4], [4, 3], [6, 2], [12, 1]]
  assert get_factors(7)==[[1, 7], [7, 1]]
output: def get_factors(n):
      factors = []
      for i in range(1, int(n**0.5) + 1):
          if n % i == 0:
              factors.append([i, n // i])
              if i != n // i:
                  factors.append([n // i, i])
      return factors