How to report an error if an element is missing in the list of lists
<p>suppose </p>

<pre><code>list1 = [['a', (1, 1)], ['a', (1, 3)], ['a', (1, 4)], ['b', (2,1)], ['b', (2,2)], ['b',(2, 4)]]

list2 = [[(1, 1), (1, 3), (2, 1), (2, 2), (2, 4)]]
</code></pre>

<p>Now how could I report an error for list1 that ['b', (1, 2)] is missing or ['b', (2, 3)] is missing  </p>

<p>Similarly for list2 there should be report error that (1, 2) or (2, 3) is missing</p>

<p>My intention is to report the error if for example something is missing in sequence like (1,1) then comes (1,2) followed by (1,3) if (1,2) is missing then error </p>
