## Documentation

- Clarify what type of graph each community detection function supports.

- Improve `read_graph` and `write_graph` documentation.

- Improve `all_simple_paths()` documentation.

- `cluster_optimal()` does support directed graphs.

## Bug fixes

- Fix the incorrect handling of the `sample` parameter in `sample_motifs()` and ensure that the default `sample.size` is integer (#1568).