code: def values_for_column(self,
                            column_name,
                            limit=10000):
          
          logging.info(
              'Getting values for columns [{}] limited to [{}]'
              .format(column_name, limit))
          # TODO: Use Lexicographic TopNMetricSpec once supported by PyDruid
          if self.fetch_values_from:
              from_dttm = utils.parse_human_datetime(self.fetch_values_from)
          else:
              from_dttm = datetime(1970, 1, 1)
  
          qry = dict(
              datasource=self.datasource_name,
              granularity='all',
              intervals=from_dttm.isoformat() + '/' + datetime.now().isoformat(),
              aggregations=dict(count=count('count')),
              dimension=column_name,
              metric='count',
              threshold=limit,
          )
  
          client = self.cluster.get_pydruid_client()
          client.topn(**qry)
          df = client.export_pandas()
          return [row[column_name] for row in df.to_records(index=False)]
docs: Retrieve some values for the given column