input: Write a function to find the maximum element in the given array. The function should return the maximum element found in the array. If the array is empty, the function should return None.
  assert find_max_element([1, 10, 50, 3, 8])==50
  assert find_max_element([3, 5, 10, 2, 8])==10
  assert find_max_element([-1, -5, -3, -2, -8])==-1
  assert find_max_element([])==None
output: def find_max_element(arr):
      if not arr:
          return None
      return max(arr)