title: Compound class selector in RobotFramework with selenium
body: <p>Trying to check the on screen state of an element which changes from :</p>
  
  <pre><code>class="slide-out-div contrastBoxDark closed"
  </code></pre>
  
  <p>to</p>
  
  <pre><code>class="slide-out-div contrastBoxDark"
  </code></pre>
  
  <p>however using</p>
  
  <pre><code>Page Should Contain Element    class:slide-out-div.contrastBoxDark
  </code></pre>
  
  <p>returns </p>
  
  <pre><code>InvalidSelectorException: Message: invalid selector: Compound class names not permitted
  </code></pre>
  
  <p>if the compound class name isn't permitted, what is a suitable locator and attribute here? Tried this, but it doesn't locate:</p>
  
  <pre><code>css:slide-out-div.contrastBoxDark
  </code></pre>