'Fetches collection of model instances of this collection property.'

def __get__(self, model_instance, model_class):

    if (model_instance is not None):
        query = Query(self.__model)
        if isinstance(self.__property, list):
            props = []
            for prop in self.__property:
                props.append(('%s    =' % prop))
            return query.filter(props, model_instance)
        else:
            return query.filter((self.__property + '    ='), model_instance)
    else:
        return self
