def is_set(self):
return all([self.start_datetime is not None, self.end_datetime is not None])<EOL>
:return:
    |True| if both |attr_start_datetime| and
    |attr_end_datetime| were not |None|.
:rtype: bool

:Sample Code:
    .. code:: python

        from datetimerange import DateTimeRange

        time_range = DateTimeRange()
        print(time_range.is_set())

        time_range.set_time_range("2015-03-22T10:00:00+0900", "2015-03-22T10:10:00+0900")
        print(time_range.is_set())
:Output:
    .. parsed-literal::

        False
        True