Format python files using yapf

Change-Id: I8b7b97efb6bfdcceef9efc533cdaa0675ab7db40
diff --git a/tools/defines.py b/tools/defines.py
index 6fdd24f..8f2cecc 100644
--- a/tools/defines.py
+++ b/tools/defines.py
@@ -12,11 +12,14 @@
 REPO_ROOT = os.path.realpath(os.path.join(TOOLS_DIR, '..'))
 THIRD_PARTY = os.path.join(REPO_ROOT, 'third_party')
 
+
 def IsWindows():
-  return sys.platform.startswith('win')
+    return sys.platform.startswith('win')
+
 
 def IsLinux():
-  return sys.platform.startswith('linux')
+    return sys.platform.startswith('linux')
+
 
 def IsOsX():
-  return sys.platform.startswith('darwin')
\ No newline at end of file
+    return sys.platform.startswith('darwin')