fixes #949L pretty format the header block xml comment

src/asammdf/blocks/v4_blocks.py

@@ -15,6 +15,7 @@
 from traceback import format_exc
 from typing import Any, TYPE_CHECKING
 import xml.etree.ElementTree as ET
+from xml.dom import minidom
 
 import dateutil.tz
 
@@ -5596,12 +5597,16 @@ def common_properties_to_xml(root, common_properties):
 
         common_properties_to_xml(common, self._common_properties)
 
-        return (
+        comment_xml = (
             ET.tostring(root, encoding="utf8", method="xml")
             .replace(b"<?xml version='1.0' encoding='utf8'?>\n", b"")
             .decode("utf-8")
         )
 
+        comment_xml = minidom.parseString(comment_xml).toprettyxml(indent=" ")
+
+        return "\n".join(comment_xml.splitlines()[1:])
+
     @comment.setter
     def comment(self, string):
         self._common_properties.clear()