input: Write a python function to find the highest number in an array using a class.
  assert HighestNumberFinder([1, 2, 3, 4, 5]).find_highest_number() == 5
  assert HighestNumberFinder([10, 20, 5, 15, 30]).find_highest_number() == 30
  assert HighestNumberFinder([3, 3, 3, 3]).find_highest_number() == 3
output: class HighestNumberFinder:
      def __init__(self, arr):
          self.arr = arr
  
      def find_highest_number(self):
          if not self.arr:
              return None
          highest = self.arr[0]
          for number in self.arr:
              if number > highest:
                  highest = number
          return highest