svg_tetraflexagon_editor.py: fix coding style

Add an expected blank line between a class and a function, reported by
pycodestyle:

  $ pycodestyle svg_tetraflexagon_editor.py
  svg_tetraflexagon_editor.py:117:1: E302 expected 2 blank lines, found 1

diff --git a/src/svg_tetraflexagon_editor.py b/src/svg_tetraflexagon_editor.py
index ce2794b..0952e8a 100755 (executable)
--- a/src/svg_tetraflexagon_editor.py
+++ b/src/svg_tetraflexagon_editor.py
@@ -114,6 +114,7 @@ class SvgwriteTetraflexagonDiagram(TetraflexagonDiagram):
 
         self.backend.active_group = old_active_group
 
+
 def main():
     width = 3508
     height = 2480