Address PR comments

src/ophyd_async/core/_device.py

@@ -84,7 +84,13 @@ def set_name(self, name: str):
             _setup_child(self, child_name, child)
 
     def __setattr__(self, name: str, value: Any) -> None:
-        if name != "parent" and isinstance(value, Device):
+        if name == "parent":
+            if self.parent not in (value, None):
+                raise TypeError(
+                    f"Cannot set the parent of {self} to be {value}: "
+                    f"it is already a child of {self.parent}"
+                )
+        elif isinstance(value, Device):
             _setup_child(self, name, value)
         return super().__setattr__(name, value)
 

src/ophyd_async/core/_signal.py

@@ -128,7 +128,11 @@ def _callback(self, reading: Reading[SignalDatatypeT]):
         for function, want_value in self._listeners.items():
             self._notify(function, want_value)
 
-    def _notify(self, function: Callback, want_value: bool):
+    def _notify(
+        self,
+        function: Callback[dict[str, Reading[SignalDatatypeT]] | SignalDatatypeT],
+        want_value: bool,
+    ):
         assert self._reading, "Monitor not working"
         if want_value:
             function(self._reading["value"])

src/ophyd_async/core/_soft_signal_backend.py

@@ -27,6 +27,9 @@
 
 
 class SoftConverter(Generic[SignalDatatypeT]):
+    # This is Any -> SignalDatatypeT because we support coercing
+    # value types to SignalDatatype to allow people to do things like
+    # SignalRW[Enum].set("enum value")
     @abstractmethod
     def write_value(self, value: Any) -> SignalDatatypeT: ...