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Adding Timestamp - ParDo
------------------------

Bounded sources (such as a file from TextIO) do not provide timestamps for elements. If you need 
timestamps, you must add them to your PCollection’s elements.

You can assign new timestamps to the elements of a PCollection by applying a ParDo transform that 
outputs new elements with timestamps that you set.

**Kata:** Please assign each element a timestamp based on the the `Event.timestamp`.

<div class="hint">
  Use <a href="https://beam.apache.org/releases/pydoc/current/apache_beam.transforms.core.html#apache_beam.transforms.core.ParDo">
  ParDo</a> with
  <a href="https://beam.apache.org/releases/pydoc/current/apache_beam.transforms.core.html#apache_beam.transforms.core.DoFn">DoFn</a>.
</div>

<div class="hint">
  Use <a href="https://beam.apache.org/releases/pydoc/current/apache_beam.transforms.window.html#apache_beam.transforms.window.TimestampedValue">
  beam.window.TimestampedValue</a> to assign timestamp to the element.
</div>

<div class="hint">
  Refer to the Beam Programming Guide
  <a href="https://beam.apache.org/documentation/programming-guide/#adding-timestamps-to-a-pcollections-elements">
    "Adding timestamps to a PCollection’s elements"</a> section for more information.
</div>
