muenchian grouping in the second level
问题 This is my xml input <issues> <issue status="open" type="Bug"> <fix_versions> <fix_version>6.14.0</fix_version> <fix_version>6.13.0</fix_version> <fix_version>6.12.0</fix_version> </fix_versions> <title>issue1</title> <description>Description</description> </issue> <issue status="open" type="Feature"> <fix_versions> <fix_version>6.13.0</fix_version> </fix_versions> <title>issue2</title> <description>Description</description> </issue> <issue status="open" type="Improvement"> <fix_versions>