* **dag:** add validators for DAG and DAGTask ([0fa1de8](https://github.com/ladybug-tools/queenbee/commit/0fa1de84ec67f051775cdf65f17c380a5842b9c0)), closes [#32](https://github.com/ladybug-tools/queenbee/issues/32)
* **function:** return null if no inputs are provided ([1be96ba](https://github.com/ladybug-tools/queenbee/commit/1be96ba9d519aa40854d5f0269390199d6e9f1f9)) * **pydantic:** bump to v1.0 ([cbf9cae](https://github.com/ladybug-tools/queenbee/commit/cbf9caede8ceb5bd54347813e2f4cb8df51d8dfc)), closes [#22](https://github.com/ladybug-tools/queenbee/issues/22)