q.addFilter(EMAIL_PROPERTY, FilterOperator.EQUAL, email);
q.addFilter(DEPT_PROPERTY, FilterOperator.EQUAL, dept);
q.addFilter(COURSE_PROPERTY, FilterOperator.EQUAL, course);
q.addFilter(SECTION_PROPERTY, FilterOperator.EQUAL, section);
PreparedQuery pq = datastore.prepare(q);
Iterator<Entity> it = pq.asIterable().iterator();
while(it.hasNext())
datastore.delete(it.next().getKey());
}