code: def _loadColumns(self, record, columnName, value):
          
          value = unwrapNone(value)
          item = self.findRecordItem(record)
          if item:
              item.updateColumnValue(record.schema().column(columnName),
                                     value,
                                     self.column(columnName))
docs: Loads the column information for this tree widget for the given record.
          
          :param      record      | <orb.Table>
                      columnName  | <str>
                      value       | <variant>