title: Collect a list of pairs into a map
body: <p>How can we collect a list of lists of value pairs into a map where said pairs are transformed into <code>key:value</code> entries in the map, as in:</p>
  
  <pre><code>a = [[1,11], [2,22], [3,33]]
  b = ...?
  assert b == [1:11, 2:22, 3:33]
  </code></pre>