删除一些不必要的代码，添加一些注释

chenshijun

2019-04-22 d5ae54ceb9770963fbe88aa0170c08d0ae648b05

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
aeroplane
bicycle
bird
boat
bottle
bus
car
cat
chair
cow
diningtable
dog
horse
motorbike
person
pottedplant
sheep
sofa
train
tvmonitor