title: splitting a list of sentences into separate words in a list
body: <p>I have a list which consists of lines as</p>
  
  <pre><code>lines =  ['The query complexity of estimating weighted averages.',
       'New bounds for the query complexity of an algorithm that learns',
       'DFAs with correction equivalence queries.',
       'general procedure to check conjunctive query containment.']
  </code></pre>
  
  <p>I need to store it in the list as 'Separate words'</p>
  
  <pre><code>lines =  ['The','query', 'complexity' ,'of' ,'estimating', 'weighted','averages.'
       ,'New' ......]
  </code></pre>
  
  <p>How to obtain it as a list of separate words?</p>