Update documentation

Author: AllenDowney

_sources/chap09.ipynb

@@ -2405,7 +2405,7 @@
    "id": "8fc79a2f",
    "metadata": {},
    "source": [
-    "Of if you want them in a string, you can use the `join` method."
+    "Or if you want them in a string, you can use the `join` method."
    ]
   },
   {

chap09.html

@@ -1364,7 +1364,7 @@ <h3><span class="section-number">9.15.3. </span>Exercise<a class="headerlink" hr
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 </div>
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-<p>Of if you want them in a string, you can use the <code class="docutils literal notranslate"><span class="pre">join</span></code> method.</p>
+<p>Or if you want them in a string, you can use the <code class="docutils literal notranslate"><span class="pre">join</span></code> method.</p>
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 <div class="highlight-ipython3 notranslate"><div class="highlight"><pre><span></span><span class="s1">&#39;&#39;</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="nb">reversed</span><span class="p">(</span><span class="s1">&#39;parrot&#39;</span><span class="p">))</span>