title: Scala, Spark-shell, Groupby failing
body: <p>I have Spark version 2.4.0 and scala version 2.11.12.  I can sucessfully load a dataframe with the following code.</p>
  
  <pre><code>val df = spark.read.format("csv").option("header","true").option("delimiter","|").option("mode","DROPMALFORMED").option("maxColumns",60000).load("MAR18.csv")
  </code></pre>
  
  <p>However, when I attempt to do a groupby the following I get an error.</p>
  
  <pre><code>df.groupby("S0102_gender").agg(sum("Respondent.Serial")).show()
  </code></pre>
  
  <p>The error message is: </p>
  
  <blockquote>
    <p>error: value groupby is not a member of org.apache.spark.sql.DataFrame</p>
  </blockquote>
  
  <p>What am I missing.  A complete Scala and Spark Newb.</p>