Add a simple version to fill the unique needs of slit4

src/dodal/beamlines/i22.py

@@ -16,7 +16,7 @@
 from dodal.devices.i22.fswitch import FSwitch
 from dodal.devices.i22.nxsas import NXSasMetadataHolder, NXSasOAV, NXSasPilatus
 from dodal.devices.linkam3 import Linkam3
-from dodal.devices.slits import Slits
+from dodal.devices.slits import Slits, SlitWithDefiningSlitOpening
 from dodal.devices.synchrotron import Synchrotron
 from dodal.devices.tetramm import TetrammDetector
 from dodal.devices.undulator import Undulator
@@ -234,13 +234,14 @@ def slits_3(
     )
 
 
-@skip_device()
 def slits_4(
     wait_for_connection: bool = True,
     fake_with_ophyd_sim: bool = False,
-) -> Slits:
-    return numbered_slits(
-        4,
+) -> SlitWithDefiningSlitOpening:
+    return device_instantiation(
+        SlitWithDefiningSlitOpening,
+        "slits_4",
+        "-AL-SLITS-04:",
         wait_for_connection,
         fake_with_ophyd_sim,
     )

src/dodal/devices/slits.py

@@ -15,3 +15,19 @@ def __init__(self, prefix: str, name: str = "") -> None:
             self.x_centre = Motor(prefix + "X:CENTRE")
             self.y_centre = Motor(prefix + "Y:CENTRE")
         super().__init__(name)
+
+
+class SlitWithDefiningSlitOpening(StandardReadable):
+    """
+    these are unlikely to be moved during a scan
+    Only HDSO and VDSO are recorded in the scan
+    DSO means Defining Slit Opening
+    """
+
+    def __init__(self, prefix: str, name: str = "") -> None:
+        with self.add_children_as_readables():
+            self.x_gap = Motor(prefix + "HDSO")
+            self.y_gap = Motor(prefix + "VDSO")
+            self.x_centre = Motor(prefix + "X")
+            self.y_centre = Motor(prefix + "Y")
+        super().__init__(name)

tests/common/beamlines/test_beamline_utils.py

@@ -59,7 +59,7 @@ def test_instantiating_different_device_with_same_name():
         Smargon, "device", "", False, True, None
     )
     assert dev1.name == dev2.name
-    assert type(dev1) is not type(dev2)
+    assert not isinstance(dev2, type(dev1))
     assert dev1 not in beamline_utils.ACTIVE_DEVICES.values()
     assert dev2 in beamline_utils.ACTIVE_DEVICES.values()