title: Group By in Groovy
body: <p>I have a list of object as follows</p>
  
  <pre><code>[["GX 470","Model"],["Lexus","Make"],["Jeep","Make"],["Red","Color"],["blue","Color"]]
  </code></pre>
  
  <p>and I want to transform it to </p>
  
  <pre><code>{"Model":["GX 470"],"Make":["Lexus","Jeep"],"Color":["Red", "blue"]}
  </code></pre>
  
  <p>I tried </p>
  
  <pre><code>list.groupBy{ it[1] }
  </code></pre>
  
  <p>But that returns me</p>
  
  <pre><code>{"Model":[["GX 470","Model"]],"Make":[["Lexus","Make"],["Jeep","Make"]],"Color":[["Red","Color"],["blue","Color"]]}
  </code></pre>