title: Remove duplicate rows and keep value in columns that are non-zero
body: <p>I have a dataframe that looks like this:</p>
  <pre><code>ID  |in_tier_1 | tier_1_location |in_tier_2 | tier_2_location
  100 |1         |Sydney           |0         | 0
  100 |0         |0                |1         | Paris
  112 |0         |0                |1         | Paris
  112 |1         |NYC              |          | 
  </code></pre>
  <p>And I want to remove duplicates but keep the non-zero values in the columns</p>
  <pre><code>ID  |in_tier_1 | tier_1_location |in_tier_2 | tier_2_location
  100 |1         |Sydney           |1         | Paris
  112 |1         |NYC              |1         | Paris
  </code></pre>
  <p>I tried to groupby <code>id</code> and use the <code>.agg()</code> function but it is not working out. Can you please help?</p>