added helper functions in AGENTS.md

Author: kosiew

AGENTS.md

@@ -22,3 +22,28 @@ This repository contains Python bindings for Rust's DataFusion.
 ## Notes
 - The repository mixes Python and Rust; ensure changes build for both languages.
 - If adding new dependencies, update `pyproject.toml` and run `uv sync --dev --no-install-package datafusion`.
+
+## Helper Functions
+- `python/datafusion/io.py` offers global context readers:
+  - `read_parquet`
+  - `read_json`
+  - `read_csv`
+  - `read_avro`
+- `python/datafusion/user_defined.py` exports convenience creators for user-defined functions:
+  - `udf` (scalar)
+  - `udaf` (aggregate)
+  - `udwf` (window)
+  - `udtf` (table)
+- `python/datafusion/col.py` exposes the `Col` helper with `col` and `column` instances for building column expressions using attribute access.
+- `python/tests/generic.py` includes utilities for test data generation:
+  - `data`
+  - `data_with_nans`
+  - `data_datetime`
+  - `data_date32`
+  - `data_timedelta`
+  - `data_binary_other`
+  - `write_parquet`
+- `python/tests/conftest.py` defines reusable pytest fixtures:
+  - `ctx` creates a `SessionContext`.
+  - `database` registers a sample CSV dataset.
+- `src/dataframe.rs` provides the `collect_record_batches_to_display` helper to fetch the first non-empty record batch and flag if more are available.