title: Represent Proto variables and constraints in python dictionary or list
body: <p>Are there any tools or libraries for representing variables and constraints in a more workable python data structure than a string (e.g. dictionary)?</p>
  <p>model.Proto().variables returns a string such as</p>
  <pre><code>[name: &quot;alice_2020&quot;
  domain: 0
  domain: 1
  , name: &quot;alice_2021&quot;
  domain: 0
  domain: 1]
  </code></pre>