input: Write a function to replace elements in an array based on specific rules: if an element is divisible by 3, replace it with "Fizz"; if an element is divisible by 5, replace it with "Buzz"; and if an element is divisible by both 3 and 5, replace it with "FizzBuzz". Return the modified array. If the input array is empty, return an empty array.
  assert fizz_buzz([2, 3, 4, 5, 6, 15])==[2, "Fizz", 4, "Buzz", "Fizz", "FizzBuzz"]
  assert fizz_buzz([1, 2, 3, 10, 15])==[1, 2, "Fizz", "Buzz", "FizzBuzz"]
  assert fizz_buzz([5, 15, 7, 8, 9])==["Buzz", "FizzBuzz", 7, 8, "Fizz"]
  assert fizz_buzz([12, 13, 14, 15, 16])==["Fizz", 13, 14, "FizzBuzz", 16]
  assert fizz_buzz([])==[]
output: def fizz_buzz(arr):
      result = []
      for num in arr:
          if num % 3 == 0 and num % 5 == 0:
              result.append("FizzBuzz")
          elif num % 3 == 0:
              result.append("Fizz")
          elif num % 5 == 0:
              result.append("Buzz")
          else:
              result.append(num)
      return result