Fix: Support recursive/nested <include> tags in MJCF parser (#529)

dm_control/mjcf/parser.py

@@ -196,7 +196,11 @@ def _parse(xml_root, escape_separators=False,
   with debugging.freeze_current_stack_trace():
     # Recursively parse any included XML files.
     to_include = []
-    for include_tag in xml_root.findall('include'):
+    # Unsloth/User Fix: Use .iter() to find ALL include tags, not just root ones.
+    # We collect them first to avoid issues while modifying the tree.
+    include_tags = list(xml_root.iter('include'))
+
+    for include_tag in include_tags:
       try:
         # First look for the path to the included XML file in the assets dict.
         path_or_xml_string = assets[include_tag.attrib['file']]
@@ -212,9 +216,15 @@ def _parse(xml_root, escape_separators=False,
           resolve_references=resolve_references,
           assets=assets)
       to_include.append(included_mjcf)
-      # We must remove <include/> tags before parsing the main XML file, since
-      # these are a schema violation.
-      xml_root.remove(include_tag)
+
+      # Remove the <include/> tag.
+      # Since we are iterating deeper, we need to find the parent to remove it.
+      parent = include_tag.getparent()
+      if parent is not None:
+          parent.remove(include_tag)
+      else:
+          # Fallback for root (though unlikely via iter unless it is self)
+          xml_root.remove(include_tag)
 
     # Parse the main XML file.
     try: