':param aggregated_activity_class: the class which we should use
for returning the aggregated activities'

def __init__(self, aggregated_activity_class=None, activity_class=None):

    if (aggregated_activity_class is not None):
        self.aggregated_activity_class = aggregated_activity_class
    if (activity_class is not None):
        self.activity_class = activity_class
