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<html>
<h2>Flatten</h2>
<p>
  Flatten is a Beam transform for PCollection objects that store the same data type.
  Flatten merges multiple PCollection objects into a single logical PCollection.
</p>
<p>
  <b>Kata:</b> Implement a
  <a href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/transforms/Flatten.html">
    Flatten</a> transform that merges two PCollection of words into a single PCollection.
</p>
<br>
<div class="hint">
  Refer to
  <a href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/transforms/Flatten.html">
    Flatten</a> to solve this problem.
</div>
<div class="hint">
  Refer to the Beam Programming Guide
  <a href="https://beam.apache.org/documentation/programming-guide/#flatten">
    "Flatten"</a> section for more information.
</div>
</html>