Function name convention did not apply

I just use yapf command and my original code has a function with violated-convention name e.g. ```Func1``` and the given command did not fix it.

```
yapf -d a.py
--- a.py (original)
+++ a.py (reformatted)
@@ -1,8 +1,12 @@
import sys
import cus.hello

-a=a+2
+a = a + 2
+
+
def Func1(a):
- return a+1
+ return a + 1
+
+
```