code: def from_db_value(self, value, expression, connection, context):
          
          # log.debug("from_db_value: {}, {}", value, type(value))
          if value is None:
              return value
          if value == '':
              return None
          return iso_string_to_python_datetime(value)
docs: Convert database value to Python value.
          Called when data is loaded from the database.