List occurrences in list of lists
<p>We have a list containing lists like so:</p>

<pre><code>My_list = [ [1,2,3],[4,5,6],[7,8,9],[1,2,3] ]
</code></pre>

<p>Is there an easy way to learn that the list item <code>[1,2,3]</code> appears twice in <code>My_list</code>? I am not interested in the individual numbers but i am interested in them as a list.</p>