```python
Disable progress bars either globally or for a specified group.

This function updates the state of progress bars based on a group name.
If no group name is provided, all progress bars are disabled. The operation
respects the `HF_HUB_DISABLE_PROGRESS_BARS` environment variable's setting.

Args:
name (`str`, *optional*):
The name of the group for which to disable the progress bars. If None,
progress bars are disabled globally.

Raises:
Warning: If the environment variable precludes changes.
```