def get_seed_users(tracks):
seed_users = set()
tmp = []
for i, t in enumerate(tracks, start=1):
tmp.append(t["url"])
if len(tmp) == 10 or i == len(tracks):
new_seeds = gevent_do(get_listening_now_users, tmp)
for group in new_seeds:
seed_users.update(set(group))
tmp = []
return seed_users