input: Write a function to find the maximum element in a given array of numbers. If the array is empty, return None.
  def find_max_element(numbers):
      if not numbers:
          return None
      max_num = numbers[0]
      for num in numbers:
          if num > max_num:
              max_num = num
      return max_num
  
  assert find_max_element([1, 43, 78, 3, 92, 42]) == 92
  assert find_max_element([34, 56, 12, 89, 45]) == 89
  assert find_max_element([5, 8, 12, 15, 19]) == 19
  assert find_max_element([]) == None
  assert find_max_element([-5, -3, -9, -1]) == -1
output: def find_max_element(numbers):
      if not numbers:
          return None
      max_num = numbers[0]
      for num in numbers:
          if num > max_num:
              max_num = num
      return max_num