input: Write a function to determine if an array has an even or odd number of elements. If the array length is even, return True, otherwise return False. If the array is empty, it should still return True since 0 is considered an even number.
  
  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