title: Django import: Ignore created value from TimeStampedModel
body: <p>I have a model which is inherited from <code>TimeStampedModel</code> and I am trying to import data using Django <code>import_export</code>.</p>
  
  <p>The imported data contains "created" column providing the datetime values which are different from current date time. The import is successful but it is using the created value from <code>TimeStampedModel</code> rather that the one from the file.</p>
  
  <p>Is there anything that can be done in the <code>import_obj</code> function to override the <code>created</code> value from the <code>TimeStampedModel</code>?
  The format of date time in the file is in the expected format and is one of the supported formats.</p>
  
  <pre class="lang-py prettyprint-override"><code>class TestResource(resources.ModelResource):
      class Meta:
          model = MyModel
  
      def import_obj(self, obj, data, dry_run):
          for field in self.get_fields():
              self.import_field(field, obj, data)
  </code></pre>
  
  <p>Object creation date is always the current <code>datetime</code> rather than the <code>datetime</code> in the imported file.</p>