title: takeOrdered descending Pyspark
body: <p>i would like to sort K/V pairs by values and then take the biggest five values. I managed to do this with reverting K/V with first map, sort in descending order with FALSE, and then reverse key.value to the original (second map) and then take the first 5 that are the bigget, the code is this:</p>
  
  <pre><code>RDD.map(lambda x:(x[1],x[0])).sortByKey(False).map(lambda x:(x[1],x[0])).take(5)
  </code></pre>
  
  <p>i know there is a takeOrdered action on pySpark, but i only managed to sort on values (and not on key), i don't know how to get a descending sorting:</p>
  
  <pre><code>RDD.takeOrdered(5,key = lambda x: x[1])
  </code></pre>