input: Write a python function to find the maximum element in an array.
  assert find_max_element([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) == 10
  assert find_max_element([10, 20, 45, 67, 84, 93]) == 93
  assert find_max_element([5, 7, 9, 8, 6, 4, 3]) == 9
output: def find_max_element(arr):
      if not arr:
          return None
      max_element = arr[0]
      for num in arr:
          if num > max_element:
              max_element = num
      return max_element