title: to_date gives null on format yyyyww (202001 and 202053)
body: <p>I have a dataframe with a yearweek column that I want to convert to a date. The code I wrote seems to work for every week except for week '202001' and '202053', example:</p>
  <pre><code>df = spark.createDataFrame([
  (1, &quot;202001&quot;), 
  (2, &quot;202002&quot;), 
  (3, &quot;202003&quot;), 
  (4, &quot;202052&quot;), 
  (5, &quot;202053&quot;)
  ], ['id', 'week_year'])
  
  df.withColumn(&quot;date&quot;, F.to_date(F.col(&quot;week_year&quot;), &quot;yyyyw&quot;)).show()
  </code></pre>
  <p>I can't figure out what the error is or how to fix these weeks. How can I convert weeks 202001 and 202053 to a valid date?</p>