input: def generate_checkered_pattern():
      """ Generate a checkered pattern of # and whitespace characters for a 7x7 grid.
      The pattern should print a # if the sum of the row and column indices is even,
      otherwise it should print a whitespace.
      >>> generate_checkered_pattern()
      # # # # # # #
       # # # # # # #
      # # # # # # #
       # # # # # # #
      # # # # # # #
       # # # # # # #
      # # # # # # # 
      """
      for i in range(7):
          for j in range(7):
              if (i + j) % 2 == 0:
                  print('#', end='')
              else:
                  print(' ', end='')
          print()
output:     for i in range(7):
          for j in range(7):
              if (i + j) % 2 == 0:
                  print('#', end='')
              else:
                  print(' ', end='')
          print()