title: pandas: Get the newest record from each group
body: <p>I have a dataframe that has the following columns:</p>
  <p><code>region</code>
  <code>target</code>
  <code>date</code>
  <code>info</code>
  <code>subinfo</code></p>
  <p>The combination of <code>'region', 'target', 'info', 'subinfo'</code> is unique in the dataframe, except when there is an older duplicate, that has the same <code>'region', 'target', 'info', 'subinfo'</code>, but different <code>date</code>.</p>
  <p>I would like to group the dataframe by <code>'region', 'target', 'info', 'subinfo'</code> and create new dataframe with only the newest records from each group / delete the records that do not have the newest date per group.</p>
  <p>How can i do that? Thank you!</p>