title: Subset list of lists based on value of element of the inner list
body: <p>I want to subset a list based on elements of one element of a sublist</p>
  
  <pre><code>inner_list1 &lt;- list(dt=iris,ver='v2')
  inner_list2 &lt;- list(dt=mtcars,ver='v1')
  outer_list &lt;- list(a=inner_list1,b=inner_list2)
  </code></pre>
  
  <p>In outer_list I want to keep the elements for which inner_list*[['ver']]=='v1'. HOw can I do that?</p>