diff --git a/src/calibre/ebooks/pdf/render/graphics.py b/src/calibre/ebooks/pdf/render/graphics.py
index f24b698350..51e2f8c407 100644
--- a/src/calibre/ebooks/pdf/render/graphics.py
+++ b/src/calibre/ebooks/pdf/render/graphics.py
@@ -18,7 +18,7 @@ from calibre.ebooks.pdf.render.common import (
 from calibre.ebooks.pdf.render.serialize import Path
 from calibre.ebooks.pdf.render.gradients import LinearGradientPattern
 
-def convert_path(path): # {{{
+def convert_path(path):  # {{{
     p = Path()
     i = 0
     while i < path.elementCount():
@@ -69,7 +69,7 @@ class TilingPattern(Stream):
 
 class QtPattern(TilingPattern):
 
-    qt_patterns = ( # {{{
+    qt_patterns = (  # {{{
         "0 J\n"
         "6 w\n"
         "[] 0 d\n"
@@ -77,7 +77,7 @@ class QtPattern(TilingPattern):
         "4 8 l\n"
         "0 4 m\n"
         "8 4 l\n"
-        "S\n", # Dense1Pattern
+        "S\n",  # Dense1Pattern
 
         "0 J\n"
         "2 w\n"
@@ -96,7 +96,7 @@ class QtPattern(TilingPattern):
         "[6 2] -3 d\n"
         "4 0 m\n"
         "4 8 l\n"
-        "S\n", # Dense2Pattern
+        "S\n",  # Dense2Pattern
 
         "0 J\n"
         "2 w\n"
@@ -115,7 +115,7 @@ class QtPattern(TilingPattern):
         "[6 2] -3 d\n"
         "4 0 m\n"
         "4 8 l\n"
-        "S\n", # Dense3Pattern
+        "S\n",  # Dense3Pattern
 
         "0 J\n"
         "2 w\n"
@@ -134,7 +134,7 @@ class QtPattern(TilingPattern):
         "[2 2] 1 d\n"
         "4 0 m\n"
         "4 8 l\n"
-        "S\n", # Dense4Pattern
+        "S\n",  # Dense4Pattern
 
         "0 J\n"
         "2 w\n"
@@ -153,7 +153,7 @@ class QtPattern(TilingPattern):
         "[2 6] 3 d\n"
         "4 0 m\n"
         "4 8 l\n"
-        "S\n", # Dense5Pattern
+        "S\n",  # Dense5Pattern
 
         "0 J\n"
         "2 w\n"
@@ -166,7 +166,7 @@ class QtPattern(TilingPattern):
         "[2 6] 3 d\n"
         "4 0 m\n"
         "4 8 l\n"
-        "S\n", # Dense6Pattern
+        "S\n",  # Dense6Pattern
 
         "0 J\n"
         "2 w\n"
@@ -175,38 +175,38 @@ class QtPattern(TilingPattern):
         "0 8 l\n"
         "8 0 m\n"
         "8 8 l\n"
-        "S\n", # Dense7Pattern
+        "S\n",  # Dense7Pattern
 
         "1 w\n"
         "0 4 m\n"
         "8 4 l\n"
-        "S\n", # HorPattern
+        "S\n",  # HorPattern
 
         "1 w\n"
         "4 0 m\n"
         "4 8 l\n"
-        "S\n", # VerPattern
+        "S\n",  # VerPattern
 
         "1 w\n"
         "4 0 m\n"
         "4 8 l\n"
         "0 4 m\n"
         "8 4 l\n"
-        "S\n", # CrossPattern
+        "S\n",  # CrossPattern
 
         "1 w\n"
         "-1 5 m\n"
         "5 -1 l\n"
         "3 9 m\n"
         "9 3 l\n"
-        "S\n", # BDiagPattern
+        "S\n",  # BDiagPattern
 
         "1 w\n"
         "-1 3 m\n"
         "5 9 l\n"
         "3 -1 m\n"
         "9 5 l\n"
-        "S\n", # FDiagPattern
+        "S\n",  # FDiagPattern
 
         "1 w\n"
         "-1 3 m\n"
@@ -217,8 +217,8 @@ class QtPattern(TilingPattern):
         "5 -1 l\n"
         "3 9 m\n"
         "9 3 l\n"
-        "S\n", # DiagCrossPattern
-    ) # }}}
+        "S\n",  # DiagCrossPattern
+    )  # }}}
 
     def __init__(self, pattern_num, matrix):
         super(QtPattern, self).__init__(pattern_num, matrix)