title: Combine lists with common elements
body: <p>Say I have for example the following nested list:</p>
  <pre><code>L = [['John','Sayyed'], ['John' , 'Simon'] ,['bush','trump'],
       ['Sam','Suri','NewYork'],['Suri','Orlando','Canada']]
  </code></pre>
  <p>How can I group these sublists, by getting the union of sublists which have a common element with at least another sublist within the group? So for the previous example, the result should be:</p>
  <pre><code>[['John','Sayyed','Simon'] ,['bush','trump'],
   ['Sam','Suri','NewYork','Orlando','Canada']]
  </code></pre>
  <p>Thus, the first two sublists are joined as they share <code>'John'</code>.
  Could someone please share their valuable thoughts?</p>