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 +1,31 @@
+from typing import Any
+
+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]
+
+  def __getitem__(self, key: Any) -> Any:
+    try:
+      link = self.node.attrs[key]
+    except KeyError:
+      raise ValueError(f"{key} link attribute not found")
+    else:
+      return self.node.root[link]

xarray_ms/backend/msv2/entrypoint.py

@@ -439,6 +439,7 @@ def open_groups_as_dict(
       antenna_factory = AntennaDatasetFactory(structure_factory)
 
       path = f"{ms_name}/partition_{p:03}"
+      ds.attrs["antenna_xds_link"] = f"{path}/ANTENNA"
       datasets[path] = ds
       datasets[f"{path}/ANTENNA"] = antenna_factory.get_dataset()