yapf formatting differs on different Python 3 version

my snippet of original code:
```python
import numbers
import posixpath
import re
```
`$ yapf -u tf_utils.py` on python conda 3.6.10, 3.7.5. 3.7.6
```bash
diff --git a/submarine-sdk/pysubmarine/submarine/utils/validation.py b/submarine-sdk/pysubmarine/submarine/utils/validation.py
index 304adac..2cf0aa3 100644
--- a/submarine-sdk/pysubmarine/submarine/utils/validation.py
+++ b/submarine-sdk/pysubmarine/submarine/utils/validation.py
@@ -16,9 +16,10 @@
Utilities for validating user inputs such as metric names and parameter names.
"""
import numbers
-import posixpath
import re

+import posixpath
+
```
- Python 3.7.6, 3.6.10 without conda would not change the code
- Python 3.6.9 without conda would not change the code as well, but it would change my other .py file.

```bash
$ cat .style.yapf

[style]
based_on_style = google
indent_width: 4
continuation_indent_width: 4
```