'Get instances and joins active during a certain time window.
:param:context: nova request context
:param:begin: datetime for the start of the time window
:param:end: datetime for the end of the time window
:param:project_id: used to filter instances by project
:param:host: used to filter instances on a given compute host
:param:expected_attrs: list of related fields that can be joined
in the database layer when querying for instances
:param use_slave if True, ship this query off to a DB slave
:param limit: maximum number of instances to return per page
:param marker: last instance uuid from the previous page
:returns: InstanceList'

@classmethod
def get_active_by_window_joined(cls, context, begin, end=None, project_id=None, host=None, expected_attrs=None, use_slave=False, limit=None, marker=None):

    begin = utils.isotime(begin)
    end = (utils.isotime(end) if end else None)
    return cls._get_active_by_window_joined(context, begin, end, project_id, host, expected_attrs, use_slave=use_slave, limit=limit, marker=marker)
