title: Python Faust Tumbling Window not working when using relative_to_field
body: <p>When the tumbling window used along with relative_to_field it is not working as expected. The values updated against a key itself are not getting reflected in the same window. It always returns the default value instead of the updated value. When I am not using &quot;relative_to_field&quot; it is working as expected.</p>
  <pre><code>import time
  from datetime import timedelta
  
  import faust
  
  class Count(faust.Record, serializer='json'):
      user: str = &quot;&quot;
      count: int = 0
      timestamp: float = 0
  
  count_schema = faust.Schema(
      key_type=str,
      value_type=Count,
      # key_serializer='str',
      value_serializer='json'
  )
  
  app = faust.App(&quot;Test_windowed_new&quot;, broker=&quot;localhost:9092&quot;, store='rocksdb://')
  count_topic = app.topic(&quot;count_topic&quot;, schema=count_schema)
  
  
  def window_processor(key, event):
      print(&quot;Windowing event 1 : {}&quot;.format(key[0]) + &quot;Event &quot; + str(event))
  
  tumbling_table = (
      app.Table(
          &quot;test_table_diff_new&quot;,
          default=Count,
          key_type=str,
          value_type=Count,
          partitions=1,
          on_window_close=window_processor,
      ).tumbling(5, key_index=True, expires=timedelta(seconds=5)).relative_to_field(Count.timestamp)
  )
  
  
  @app.agent(count_topic)
  async def count_message(msgs):
      async for key,msg in msgs.items():
          print(&quot;incoming message  &quot;+str(msg) +&quot; for key &quot; + key)
          windowSet = tumbling_table[key]
          prev_count = windowSet.value()
          count=  Count()
          count.count = msg.count + prev_count.count
          count.user=msg.user
          count.timestamp = msg.timestamp
          tumbling_table[key]= count
          print(&quot;Going to update :: &quot; + str(count) + &quot; for key &quot; + key + &quot;for log_time_in_sec  &quot; + str(msg.timestamp))
          print(&quot;Value after update :: &quot; + str(tumbling_table[key].value()) + &quot; for key &quot; + key)
  
  
  
  @app.timer(interval=1.0,  on_leader=True)
  async def send_count_kafka():
      count = Count()
      count.user = &quot;test&quot;
      count.count = 100
      count.timestamp =time.time()
      await count_message.send(
          key=str(count.user),
          value=count
      )
      print('Count Message :: send messge')
  
  if __name__ == '__main__':
      print(&quot;Test Application getting started&quot;)
      app.main()
  </code></pre>
  <h2>Expected behavior</h2>
  <p>Below Print statement where we are printing the latest value from the tumbling window after the update should return the value which has been updated in the previous step
  &quot;Value after update :: &quot; + str(tumbling_table[key].value()) &quot;</p>
  <pre><code>[2021-04-02 17:52:43,709] [29841] [WARNING] Value after update :: &lt;Count: user='test', count=100, timestamp=1617366163.204891&gt;  for key test 
  </code></pre>
  <h2>Actual behavior</h2>
  <p>Below Print statement where we are printing the latest value from the tumbling window after the update is giving the default value instead of the updated value
  &quot;Value after update :: &quot; + str(tumbling_table[key].value()) &quot;</p>
  <pre><code>[2021-04-02 17:52:43,698] [29841] [WARNING] incoming message  &lt;Count: user='test', count=100, timestamp=1617366163.204891&gt; for key test 
  [2021-04-02 17:52:43,709] [29841] [WARNING] Going to update :: &lt;Count: user='test', count=100, timestamp=1617366163.204891&gt; for key test for log_time_in_sec  1617366163.204891 
  [2021-04-02 17:52:43,709] [29841] [WARNING] Value after update :: &lt;Count: user='', count=0, timestamp=0&gt; for key test 
  </code></pre>
  <h1>Versions</h1>
  <ul>
  <li>Python version : 3.8.8</li>
  <li>Faust version : v1.10.4</li>
  <li>Operating system : OSX  Big Sur 11.2.3</li>
  <li>Kafka version : kafka_2.12-2.3.0</li>
  <li>RocksDB version : 0.7.0</li>
  </ul>
  <p>I am not sure why this simple code is not working when using relative_to_field option along with tumbling window.</p>