Update README.md

README.md

@@ -682,11 +682,10 @@ misc.has_neurips_2025_forward_model_error
 ### Advanced Usage
 Install `constellaration` from [here](https://github.com/proximafusion/constellaration).
 
-Load, instantiate and plot plasma boundaries:
+Load and instantiate plasma boundaries:
 ```python
 import datasets
 from constellaration.geometry import surface_rz_fourier
-from constellaration.utils import visualization
 
 full_json_ds = datasets.load_dataset("proxima-fusion/constellaration", "full_json")["train"]
 full_json_df = full_json_ds.to_pandas().set_index("plasma_config_id")
@@ -696,6 +695,8 @@ boundary = surface_rz_fourier.SurfaceRZFourier.model_validate_json(boundary_json
 ```
 Plot boundary:
 ```python
+from constellaration.utils import visualization
+
 visualization.plot_surface(boundary)
 visualization.plot_boundary(boundary)
 ```
@@ -706,7 +707,6 @@ Stream and instantiate the VMEC ideal MHD equilibria:
 ```python
 import datasets
 from constellaration.mhd import vmec_utils
-from constellaration.utils import visualization
 
 ds = datasets.load_dataset("proxima-fusion/constellaration", "vmecpp_ideal_mhd_equilibria", streaming=True)["train"]
 
@@ -719,10 +719,21 @@ vmecpp_wout = vmec_utils.VmecppWOut.model_validate_json(vmecpp_wout_json)
 plasma_config_id = batch["plasma_config_id"][0]
 boundary_json = full_json_df.loc[plasma_config_id]["boundary.surface"]
 boundary = surface_rz_fourier.SurfaceRZFourier.model_validate_json(boundary_json)
+```
+Plot flux surfaces:
+```python
+from constellaration.utils import visualization
 
 visualization.plot_flux_surfaces(vmecpp_wout, boundary)
 ```
 ![Plot of flux surfaces](flux_surfaces.png)
+Save ideal MHD equilibrium to VMEC2000 WOut file:
+```python
+import pathlib
+from constellaration.utils import file_exporter
+
+file_exporter.to_vmec2000_wout_file(vmecpp_wout, pathlib.Path("vmec2000_wout.nc"))
+```
 
 ## Dataset Structure
 
@@ -776,7 +787,7 @@ Proxima Fusion's stellarator optimization team.
 
 The dataset contains no personally identifiable information.
 
-## Citation [optional]
+## Citation
 
 <!-- If there is a paper or blog post introducing the dataset, the APA and Bibtex information for that should go in this section. -->
 
@@ -784,7 +795,7 @@ The dataset contains no personally identifiable information.
 
 [not published yet]
 
-## Glossary [optional]
+## Glossary
 
 <!-- If relevant, include terms and calculations in this section that can help readers understand the dataset or dataset card. -->
 
@@ -798,7 +809,7 @@ The dataset contains no personally identifiable information.
 | NAE | Near-Axis Expansion |
 | NFP | Number of Field Periods |
 
-## Dataset Card Authors [optional]
+## Dataset Card Authors
 
 Alexander Bauer, Santiago A. Cadena