title: Where is the NoneType located?
body: <p>In Python 3, I would like to check whether <code>value</code> is either string or <code>None</code>.</p>
  <p>One way to do this is</p>
  <pre><code>assert type(value) in { str, NoneType }
  </code></pre>
  <p>But where is <code>NoneType</code> located in Python?</p>
  <p>Without any import, using <code>NoneType</code> produces <code>NameError: name 'NoneType' is not defined</code>.</p>