TL;DR: networkx requires the decorator package and it is not installed. Run `pip install decorator` and networkx imports fine.

## The error
```text
ImportError: No module named decorator
```

## Fix it
1. Install decorator:
   ```
   pip install decorator
   ```
   Expected: install completes.
2. Verify:
   ```
   python -c "import networkx; print(networkx.__version__)"
   ```
   Expected: prints the version, no error.

## When this applies
Use this when `import networkx` raises the decorator error, common after --no-deps installs.

## When it does not apply
If decorator is installed but networkx still fails, check for a broken install with pip check. If the error names a different module, install that one instead.

## Compatibility
All networkx 2.x versions; decorator has always been required.

## Root cause
networkx uses the decorator package for its decorator-heavy API (notable edge-attribute decorators). The dependency is declared, but installs that skip dependencies leave it out.

## Edge cases
Very old decorator versions can break new networkx; installing normally gets a compatible one. In conda envs, install decorator from the same channel as networkx.