title: How to get all keys from a Rascal map?
body: <p>Suppose I have a map like so:</p>
  
  <pre><code>map[str,int] a = ("apple": 1, "pear": 2, "banana": 3, "kiwi": 4); 
  </code></pre>
  
  <p>Is there any way to return all the keys in the map, i.e. "apple", "pear", "banana", "kiwi"? From the documentation at <a href="http://tutor.rascal-mpl.org/Rascal/Expressions/Values/Map/Comprehension/Comprehension.html#/Rascal/Expressions/Values/Map/Map.html" rel="nofollow noreferrer">http://tutor.rascal-mpl.org/Rascal/Expressions/Values/Map/Comprehension/Comprehension.html#/Rascal/Expressions/Values/Map/Map.html</a> , it does not seem like there's a built in way. Is it possible?</p>