input: Write a function to find the maximum element in the given array. If the array is empty, return -1.
  def find_max_element(array):
      if not array:
          return -1
      return max(array)
  
  assert find_max_element([1, 10, 50, 3, 8])==50
  assert find_max_element([])==-1
output: def find_max_element(array):
      if not array:
          return -1
      return max(array)