Derived signal timeout bug

I wrote a device for the cobra on i15-1 which uses a derived signal to move it between a `safe` and `beam` position, which takes ~30s. I found when I do `bps.abs_set(derived_signal, value)` which sets the underlying motor, I get a timeout error (see https://graylog.diamond.ac.uk/messages/graylog-prod_19/99066f52-2934-11f1-a66b-22d3eb5a3de6). This seemed to happen after 10s of the move. This happened even if I gave long timeouts to the motor set call inside the `set_derived` function. If I just set the motor directly, I don't get this error so it seems like something to do with the derived signal. This is how I wrote the device: ```python class Cobra(StandardReadable): def __init__(self, prefix: str): self.motor = Motor(prefix=prefix) self.position = derived_signal_rw( self._get_position, self._set_position, current_position=self.motor, ) self._safe_position = 2.0 self._beam_position = 100.0 super().__init__(prefix) def _get_position(self, current_position: float) -> CobraPosition: if current_position == self._safe_position: return CobraPosition.SAFE elif current_position == self._beam_position: return CobraPosition.BEAM raise ValueError( f"Device's position {current_position} is not {CobraPosition.SAFE}: " f"{self._safe_position} or {CobraPosition.BEAM}: {self._beam_position}" ) async def _set_position(self, position: CobraPosition): if position == CobraPosition.SAFE: await self.motor.set(self._safe_position, 60) elif position == CobraPosition.BEAM: await self.motor.set(self._beam_position, 60) ``` ```python yield from bps.abs_set(cobra.position, CobraPosition.SAFE, group=group) # TimeoutError yield from bps.abs_set(cobra.motor, 2.0, group=group) # works ``` ## Steps To Reproduce Steps to reproduce the behaviour: 1. Create a derived signal who's set method takes longer than 10s 2. Call `bps.abs_set` on the derived signal. ## Acceptance Criteria - You can have a derived signal who's set method takes longer than 10s