Add Instrument.group_name_to_group_id method

This supports visit definition from group dimension.

doc/changes/DM-42636.feature.rst

@@ -0,0 +1 @@
+Added ``Instrument.group_name_to_group_id`` method to convert a group name string to an integer suitable for use as a visit ID.

python/lsst/pipe/base/_instrument.py

@@ -32,6 +32,7 @@
 import contextlib
 import datetime
 import os.path
+import re
 from abc import ABCMeta, abstractmethod
 from collections.abc import Sequence
 from typing import TYPE_CHECKING, Any, cast, final
@@ -735,3 +736,27 @@ def _make_default_dimension_packer(
             IDs into integers.
         """
         return config_dict.apply_with(default, data_id, is_exposure=is_exposure)
+
+    @classmethod
+    def group_name_to_group_id(cls, group_name: str) -> int:
+        """Translate the exposure group name to an integer.
+
+        Parameters
+        ----------
+        group_name : `str`
+            The name of the exposure group.
+
+        Returns
+        -------
+        id : `int`
+            The exposure group name in integer form. This integer might be
+            used as an ID to uniquely identify the group in contexts where
+            a string can not be used.
+
+        Notes
+        -----
+        The default implementation removes all non numeric characters and casts
+        to an integer.
+        """
+        cleaned = re.sub(r"\D", "", group_name)
+        return int(cleaned)

tests/test_instrument.py

@@ -325,6 +325,12 @@ def check_dimension_packers(
                 with self.assertRaisesRegex(ValueError, f"Exposure ID {n_exposures} is out of bounds"):
                     packer.pack(instrument=self.name, detector=1, exposure=n_exposures)
 
+    def test_group_name(self):
+        """Test group name to ID conversion."""
+        self.assertEqual(self.instrument.group_name_to_group_id("1:234-5.6"), 123456)
+        with self.assertRaises(ValueError):
+            self.instrument.group_name_to_group_id("no_int")
+
 
 if __name__ == "__main__":
     unittest.main()