added xml prolog

__init__.py

@@ -0,0 +1 @@
+# intentionally empty

modules/pcgenerator.py

@@ -139,7 +139,7 @@ class PCGenerator:
 		for i in sorted_objects:
 			diagram.add(i)
 
-		return diagram.tostring()
+		return '<?xml version="1.0" encoding="UTF-8" standalone="no"?>{}'.format(diagram.tostring())
 
 	def create_card(self):
 

test/__init__.py

@@ -0,0 +1 @@
+# intentionally empty

test/test.py

@@ -1,4 +1,7 @@
-from pcgenerator import PCGenerator
+# invocation: python -m test.test
+
+from modules.pcgenerator import PCGenerator
+
 pattern='-x--\n-xxx\nxxx-\n--x-\n'
 machine = '12-stitch-br-sr'
 #machine = '24-stitch-br-sr'