def get_value_for_datastore(self, model_instance):
    value = super(DateProperty, self).get_value_for_datastore(model_instance)
    if value is not None:
      assert isinstance(value, datetime.date)
      value = _date_to_datetime(value)
    return value
Given a line with an Eliot message, it inserts the hostname
dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/ext/db/__init__.py/DateProperty.get_value_for_datastore--crossover with--dataset/ETHPy150Open ClusterHQ/flocker/admin/acceptance.py/TailFormatter.parse_line