TL;DR: numba needs the llvmlite package and it is not installed. Run `pip install llvmlite` (or reinstall numba, which pulls it in) and the import works.

## The error
```text
ModuleNotFoundError: No module named 'llvmlite'
```

## Fix it
1. Install llvmlite:
   ```
   pip install llvmlite
   ```
   Expected: install completes.
2. Verify:
   ```
   python -c "import numba; print(numba.__version__)"
   ```
   Expected: prints the version, no error.
3. If it still fails, reinstall numba so pip resolves the pair together:
   ```
   pip install --force-reinstall numba
   ```

## When this applies
Use this when `import numba` raises the llvmlite error, common after a partial install or a botched upgrade.

## When it does not apply
If llvmlite is installed but numba still fails, the versions may be mismatched; reinstall both together. If the error names a different module, that is a separate issue.

## Compatibility
All numba versions; each numba release requires a specific llvmlite version, so install them as a pair.

## Root cause
numba compiles Python to machine code through LLVM, and llvmlite is its LLVM binding layer. It is a hard dependency, but partial installs and --no-deps installs can leave it out.

## Edge cases
On conda, install both from conda-forge to keep the LLVM builds consistent. Very new Python versions may need a newer numba/llvmlite pair than your pins allow.