This commit makes to use sequence directly instead of using
len(SEQUENCE). The original code works correctly, and it's really
straight forward. However, PEP8 recommends like below[1]. And it
makes code more simple, too.
```
For sequences, (strings, lists, tuples), use the fact that empty
sequences are false.
Yes: if not seq:
if seq:
No: if len(seq):
if not len(seq):
```
[1] https://www.python.org/dev/peps/pep-0008/#programming-recommendations
Change-Id: I8d41e16d82b1b3860a98e5217cb7a541fc83b907
0c0f0143e1