title: General::ivar: ... is not a valid variable
body: <p>I have been trying to decipher what this output means, but I just can't seem to figure it out. Does anybody know what is going on here?</p>
  
  <p><img src="https://i.stack.imgur.com/0W43U.png" alt="alt text"></p>
  
  <p>I have even tried running the lines one by one and the errors only show up when the final line (show) is executed.</p>