change examples of flatten and collect

Author: toy

_overviews/cheatsheets/index.md

@@ -471,8 +471,8 @@ println(upper.getOrElse(""))</code></pre></td>
       <td><pre class="highlight"><code>optionOfOption.flatten</code></pre>
       <em><strong>same as</strong></em>
       <pre class="highlight"><code>optionOfOption match {
-  case Some(Some(x)) =&gt; Some(x)
-  case _             =&gt; None
+  case Some(x: Option[_]) =&gt; x
+  case None               =&gt; None
 }</code></pre></td>
       <td>Extract nested option.</td>
     </tr>
@@ -503,8 +503,7 @@ println(upper.getOrElse(""))</code></pre></td>
       <pre class="highlight"><code>option match {
   case Some(x)
     if f.isDefinedAt(x) =&gt; ...
-  case Some(_)          =&gt; None
-  case None             =&gt; None
+  case _                =&gt; None
 }</code></pre></td>
       <td>Apply partial pattern match on optional value</td>
     </tr>