input: 
  def print_chessboard(n: int) -> None:
      """Prints an n x n chessboard pattern using '#' and spaces.
      >>> print_chessboard(7)
      # # # # # # # 
       # # # # # # #
      # # # # # # # 
       # # # # # # #
      # # # # # # # 
       # # # # # # #
      # # # # # # # 
      """
      for i in range(n):
          for j in range(n):
              if (i + j) % 2 == 0:
                  print('#', end='')
              else:
                  print(' ', end='')
          print()
  
output:     for i in range(n):
          for j in range(n):
              if (i + j) % 2 == 0:
                  print('#', end='')
              else:
                  print(' ', end='')
          print()