Why double check world_size==1 in comm.py

[serend1p1ty]

Hello, detectron2 is great!
However, I have confusion when reading the source code of comm.py.

Here, why double check world_size==1 ?

detectron2/detectron2/utils/comm.py

Line 116 in cc87e7e

if world_size == 1:

[serend1p1ty]

I see, because the world_size of the user-specified group maybe not be equal to the world_size of the default global group.