Why do I not see linux name spaces for my warden instances?

root(a)874c4cea-19ed-41c7-abd2-09eb5851d54d:/var/vcap/data/warden/depot# ip netns list <-- note that the output was blank
root(a)874c4cea-19ed-41c7-abd2-09eb5851d54d:/var/vcap/data/warden/depot# ls
19b0ug03pal 19b0ug03pba tmp <-- however, there are two containers up and running