title: How can I hide cell contents in Google Colaboratory?
body: <p>I'm working through a tutorial in Google Colaboratory, and the author has handily hidden some of the solutions cells.  When you click the hidden cell, it expands and becomes visible.  How can I hide the cells?</p>
  
  <p>An example is in this tutorial:  <a href="https://colab.research.google.com/notebooks/mlcc/creating_and_manipulating_tensors.ipynb?hl=en" rel="noreferrer">Creating and Manipulating Tensors</a>.</p>
  
  <p><a href="https://i.stack.imgur.com/fNwV0.png" rel="noreferrer"><img src="https://i.stack.imgur.com/fNwV0.png" alt="Hidden Cells example"></a></p>