code: def _build_time_fields_spec(name_in_context: str) -> List[Dict[str, Any]]:
          
          return [
              {
                  'Name': '_start_time',
                  'Type': Type.DATETIME,
                  'Value': ('time if {aggregate}._start_time is None else time '
                            'if time < {aggregate}._start_time else {aggregate}._start_time'
                            ).format(aggregate=name_in_context),
                  ATTRIBUTE_INTERNAL: True
              },
              {
                  'Name': '_end_time',
                  'Type': Type.DATETIME,
                  'Value': ('time if {aggregate}._end_time is None else time '
                            'if time > {aggregate}._end_time else {aggregate}._end_time'
                            ).format(aggregate=name_in_context),
                  ATTRIBUTE_INTERNAL: True
              },
          ]
docs: Constructs the spec for predefined fields that are to be included in the master spec prior to schema load
          :param name_in_context: Name of the current object in the context
          :return: