title: Grouping the message based on one field in mule data weaver
body: <p>I have a requirement where I want to filter the incoming message based on the category='E'. So if the category = 'I', it should be trimmed off the message.</p>
  
  <h2>Sample Input</h2>
  
  <pre><code>&lt;DataSet&gt;
      &lt;SubDataSet&gt;
          &lt;DataNum&gt;TEXU9022186&lt;/DataNum&gt;
          &lt;Category&gt;E&lt;/Category&gt;                             
      &lt;/SubDataSet&gt;
      &lt;SubDataSet&gt;
          &lt;DataNum&gt;TEXU9022186T&lt;/DataNum&gt;
          &lt;Category&gt;I&lt;/Category&gt;                                  
      &lt;/SubDataSet&gt;
      &lt;SubDataSet&gt;
          &lt;DataNum&gt;TEXU9022186T&lt;/DataNum&gt;
          &lt;Category&gt;E&lt;/Category&gt;
      &lt;/SubDataSet&gt;
  &lt;/DataSet&gt;
  </code></pre>
  
  <h2>Sample Output</h2>
  
  <pre><code>&lt;DataSet&gt;
      &lt;SubDataSet&gt;
          &lt;DataNum&gt;TEXU9022186&lt;/DataNum&gt;
          &lt;Category&gt;E&lt;/Category&gt;                             
      &lt;/SubDataSet&gt;
      &lt;SubDataSet&gt;
          &lt;DataNum&gt;TEXU9022186T&lt;/DataNum&gt;
          &lt;Category&gt;E&lt;/Category&gt;                                  
      &lt;/SubDataSet&gt;
  &lt;/DataSet&gt;
  </code></pre>
  
  <p>Could you please how to achieve this by mule dataweaver</p>