TL;DR: your msmexplorer is too old for your seaborn. seaborn removed the private _scipy_univariate_kde helper, so upgrade msmexplorer to a release that no longer uses it, or pin an older seaborn.

## The error
```text
ImportError: cannot import name '_scipy_univariate_kde' from 'seaborn.distributions'
```

## Fix it
1. Upgrade msmexplorer:
   ```
   pip install -U msmexplorer
   ```
   Expected: installs a release fixed for modern seaborn.
2. Verify:
   ```
   python -c "import msmexplorer; print('ok')"
   ```
   Expected: imports cleanly.
3. Workaround if you cannot upgrade msmexplorer: pin seaborn below the removal:
   ```
   pip install "seaborn<0.12"
   ```
   Expected: the private name exists again.

## When this applies
Use this when `import msmexplorer` raises this error with a recent seaborn.

## When it does not apply
If your own code imports the private helper, vendor a KDE implementation instead of depending on seaborn internals. If msmexplorer is current, reinstall it.

## Compatibility
msmexplorer releases before the seaborn-compat fix; seaborn 0.12+ where the helper is gone.

## Root cause
_scipy_univariate_kde was a private (underscore-prefixed) helper inside seaborn.distributions, never public API. seaborn removed it during cleanup, and msmexplorer imported it directly, so msmexplorer broke at import time.

## Edge cases
Pinning old seaborn can break other packages that need new seaborn; upgrading msmexplorer is the durable fix. Private-name imports are always at risk; treat any of them as a bug in the importing package.