input: Write a function to check whether an array has an even or odd number of elements. If the number of elements in the given array is even return True else return False. If the given array is empty then consider it as even and return True.
  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