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(numbers):
      if not numbers:
          return None
      return max(numbers)
  
  assert find_max([1, 43, 78, 3, 92, 42])==92
  assert find_max([3, 6, 8, 2, 4])==8
  assert find_max([42])==42
  assert find_max([])==None
output: def find_max(numbers):
      if not numbers:
          return None
      return max(numbers)