I installed it without -e option, but I got cannot import name 'constants' error.

I tried to install this repository as follows:

```
git clone https://github.com/deepmind/dm_control.git
cd dm_control/
pip3 install -r requirements.txt
```

But, after running the command, the following error occurred.

```
python3 ./dm_control/locomotion/soccer/explore.py
ImportError: cannot import name 'constants' from partially initialized module 'dm_control.mujoco.wrapper.mjbindings' (most likely due to a circular import) (/home/dl/DM_Control2/dm_control/dm_control/mujoco/wrapper/mjbindings/__init__.py)
```

Please let me know how to avoid it.

首先复现 requirements.txt 中的命令并运行 dm_control/locomotion/soccer/explore.py。然后检查 dm_control/mujoco/wrapper/mjbindings/__init__.py 和报告的导入路径，以确定 constants 无法使用的原因；完成的标准是确认安装或导入修正，并记录经过验证的结果。

由索引模型根据 Issue 内容生成。