input: Write a function to check whether an array has an even or odd number of elements. If the number of elements is even, return True, otherwise return False. If the array is empty, return True since zero is an even number.
  def is_array_even(arr): 
    if len(arr)%2 == 0:
      return True
    else:
      return False
  assert is_array_even([1, 2, 3, 4])==True
  assert is_array_even([1, 2, 3])==False
  assert is_array_even([])==True
output: def is_array_even(arr): 
    return len(arr) % 2 == 0