Experiment with accessors and links in attributes

xarray_ms/__init__.py

@@ -0,0 +1 @@
+import xarray_ms.accessors  #  noqa: F401

xarray_ms/accessors.py

@@ -0,0 +1,21 @@
+from xarray.core.datatree import DataTree
+from xarray.core.extensions import (
+  register_datatree_accessor,
+)
+
+
+@register_datatree_accessor("subtable")
+class SubTableAccessor:
+  def __init__(self, node: DataTree):
+    self.node = node
+
+  @property
+  def antenna(self) -> DataTree:
+    """Returns the antenna dataset"""
+
+    try:
+      link = self.node.attrs["antenna_xds_link"]
+    except KeyError:
+      raise ValueError("antenna_xds_link not found")
+    else:
+      return self.node.root[link]

xarray_ms/backend/msv2/entrypoint.py

@@ -375,6 +375,7 @@ def open_datatree(
       antenna_factory = AntennaDatasetFactory(structure_factory)
 
       key = ",".join(f"{k}={v}" for k, v in sorted(partition_key))
+      ds.attrs["antenna_xds_link"] = f"{key}/ANTENNA"
       datasets[key] = ds
       datasets[f"{key}/ANTENNA"] = antenna_factory.get_dataset()