title: Split string value of a dictionary
body: <p>I have this dictionary:</p>
  
  <pre><code>{
      1: '1 2',
      2: '2 3',
      3: '2 3',
      ...
  }
  </code></pre>
  
  <p>And I want to separate the value of each key to a list of individual elements
  So I want it to look like this:</p>
  
  <pre><code>{
      1: [1,2],
      2: [2,3],
      ...
  }
  </code></pre>