input: Write a python function to calculate the power of a number iteratively.
  assert power_iterative(2, 3) == 8
  assert power_iterative(5, 0) == 1
  assert power_iterative(7, 2) == 49
  assert power_iterative(10, 1) == 10
output: def power_iterative(base, exponent):
      result = 1
      for _ in range(exponent):
          result *= base
      return result