title: Convert list of maps into one single map
body: <p>How could a list of maps like <code>some_maps = [%{"test" =&gt; [1]}, %{"test2" =&gt; [2]}, %{"test" =&gt; [3]}]</code> be converted to one huge single map with it's values merged?</p>
  
  <pre><code>single_map = %{"test" =&gt; [1, 3], "test2" =&gt; [2]}
  </code></pre>
  
  <p>Since I cannot modify a map within an iteration like <code>for</code> I dont know how to build this map</p>
  
  <p>In other language I would define an empty map and iterate through the list and fill the map but functionally thinking I dont see how I could do this.</p>