input: Write a function to check whether an array has an even or odd number of elements. If the array has an even number of elements, return True; otherwise, return False.
  
  assert is_array_even([1, 2, 3, 4]) == True
  assert is_array_even([1, 2, 3]) == False
  assert is_array_even([]) == True
  assert is_array_even([1]) == False
  assert is_array_even([1, 2, 3, 4, 5, 6]) == True
output: def is_array_even(arr):
      return len(arr) % 2 == 0