title: Getting the value or index of Combobox item?
body: <p>I am trying to make my GUI display information depending on the item chosen in the combobox. <code>PySimpleGUI</code> cookbook says that I should be using <code>GetSelectedItemsIndexes()</code> method, but when I try using it:</p>
  
  <pre><code>window.Element('_COMBOBOX_').GetSelectedItemsIndexes()
  </code></pre>
  
  <p>I get this:</p>
  
  <blockquote>
    <p>AttributeError: 'Combo' object has no attribute 'GetSelectedItemsIndexes'</p>
  </blockquote>
  
  <p>I tried type this into the console:</p>
  
  <pre><code>dir(window.Element('_COMBOBOX_'))
  </code></pre>
  
  <p>and it seems that <code>GetSelectedItemsIndexes</code> is not even there... So how can I get the index of a chosen value from combobox?</p>