input: def print_checkerboard(size: int) -> None:
      """Prints a checkerboard pattern of given size.
      >>> print_checkerboard(3)
      # #
       # 
      # #
      >>> print_checkerboard(4)
      # # 
       # #
      # # 
       # #
      """
      for i in range(size):
          for j in range(size):
              if (i + j) % 2 == 0:
                  print('#', end='')
              else:
                  print(' ', end='')
          print()
output:     for i in range(size):
          for j in range(size):
              if (i + j) % 2 == 0:
                  print('#', end='')
              else:
                  print(' ', end='')
          print()