title: OCaml map a string to a list of strings
body: <p>I'm trying to create a dictionary in OCaml that maps a string to a list of strings. I've referenced <a href="https://ocaml.org/learn/tutorials/map.html" rel="nofollow">this</a> tutorial for a basic string to string map, but I need some help making a list.</p>
  
  <p>Here is what I want to do in Python:</p>
  
  <pre><code>&gt;&gt;&gt; food = {}
  &gt;&gt;&gt; food["fruit"] = ("blueberry", "strawberry", "kiwi")
  &gt;&gt;&gt; food["veggie"] = ("broccoli", "kale")
  &gt;&gt;&gt; for k in food:
  ...     for v in food[k]:
  ...         print k, "--&gt;",v
  ...
  fruit --&gt; blueberry
  fruit --&gt; strawberry
  fruit --&gt; kiwi
  veggie --&gt; broccoli
  veggie --&gt; kale
  </code></pre>
  
  <p>Thanks in advance</p>