TL;DR: you have two seaborn installs (usually one from conda and one from pip) fighting in one environment. Remove every copy, then install seaborn exactly once.

## The error
```text
ImportError: cannot import name 'QUAL_PALETTES'
```

## Fix it
1. Remove seaborn with both installers, repeatedly until both say it is gone:
   ```
   pip uninstall -y seaborn
   conda remove -y seaborn
   ```
   Repeat until `pip show seaborn` and `conda list seaborn` both report nothing.
2. Install exactly once. Pick one:
   ```
   pip install seaborn
   ```
   or `conda install -c conda-forge seaborn`. Expected: a single install.
3. Verify:
   ```
   python -c "import seaborn; print(seaborn.__version__)"
   ```
   Expected: prints the version, no error.

## When this applies
Use this when `import seaborn` raises the QUAL_PALETTES error and the env mixes conda and pip installs.

## When it does not apply
If only one installer ever touched the env, the install may just be corrupt; a single reinstall suffices. If the error names a different symbol, check version compatibility instead.

## Compatibility
Any seaborn version; this is an environment-hygiene issue.

## Root cause
seaborn's _core module imports QUAL_PALETTES from its own palettes module. With two versions' files interleaved in site-packages, the import machinery assembles a Frankenstein package whose modules do not match, and the name lookup fails.

## Edge cases
After cleanup, audit other packages for the same double-install pattern (matplotlib and numpy are frequent repeat offenders). Prefer one installer per environment going forward.