def _datetime_from_json(value, field):
 if _not_null(value, field):
  return datetime.datetime.strptime(value, _RFC3339_NO_FRACTION)

def _datetime_from_json ( value , field ) : if _not_null ( value , field ) : return datetime . datetime . strptime ( value , _RFC3339_NO_FRACTION )
coerce value to a datetime .