Unable to load an .xml with bodies which have "user" parameter using "mjcf.from_path()"

Hi, I'm a student and I'm trying to use MuJoCo for simulating rigid body dynamics.

I'm looking for some help with setting "user" attribute in "body" elements in .XML files. Reading [this section](https://mujoco.readthedocs.io/en/stable/modeling.html#user-parameters) and referring to [these lines](https://github.com/google-deepmind/mujoco/blob/7d3b662d5b3e3c3f6cf9ed3f17f3ab4dda4923f3/test/user/user_objects_test.cc#L1188), I tried to set a user parameter as follows:

```XML

minimal


```

But I got the following error:
```
Traceback (most recent call last):
File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/parser.py", line 210, in _parse_children
mjcf_child = mjcf_element.add(xml_child.tag, **attributes)
File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 630, in add
return self.insert(element_name, position=None, **kwargs)
File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 655, in insert
new_element = _make_element(child_spec, self, attributes=kwargs)
File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 128, in _make_element
return _ElementImpl(spec, parent, attributes)
File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 185, in __init__
self._check_valid_attribute(attribute_name)
File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 534, in _check_valid_attribute
raise AttributeError(
AttributeError: 'user' is not a valid attribute for

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "", line 1, in
File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/parser.py", line 104, in from_path
return _parse(xml_root, escape_separators,
File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/parser.py", line 169, in _parse
_parse_children(xml_root, mjcf_root, escape_separators)
File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/parser.py", line 219, in _parse_children
_parse_children(xml_child, mjcf_child, escape_separators)
File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/parser.py", line 216, in _parse_children
raise err_type(
File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/parser.py", line 210, in _parse_children
mjcf_child = mjcf_element.add(xml_child.tag, **attributes)
File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 630, in add
return self.insert(element_name, position=None, **kwargs)
File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 655, in insert
new_element = _make_element(child_spec, self, attributes=kwargs)
File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 128, in _make_element
return _ElementImpl(spec, parent, attributes)
File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 185, in __init__
self._check_valid_attribute(attribute_name)
File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 534, in _check_valid_attribute
raise AttributeError(
AttributeError: Line 4: error while parsing element : 'user' is not a valid attribute for
```

Does `mjcf` support .XML files with "body" elements with a "user" parameter in the first place? If it supports, which part should I change in the XML string above?

Thanks in advance,