Make _ActorInfo generic

When using an union, if we want to use a method present only in one of
the union types, then we need to assert for the type, so it is better
to just make it generic to the type is always the specific type.

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

src/frequenz/sdk/microgrid/_data_pipeline.py

@@ -50,12 +50,14 @@
 requests and will be able to keep up with higher request rates in larger installations.
 """
 
+_T = typing.TypeVar("_T")
+
 
 @dataclass
-class _ActorInfo:
+class _ActorInfo(typing.Generic[_T]):
     """Holds instances of core data pipeline actors and their request channels."""
 
-    actor: "DataSourcingActor | ComponentMetricsResamplingActor"
+    actor: _T
     channel: Broadcast["ComponentMetricRequest"]
 
 
@@ -82,8 +84,10 @@ def __init__(
 
         self._channel_registry = ChannelRegistry(name="Data Pipeline Registry")
 
-        self._data_sourcing_actor: _ActorInfo | None = None
-        self._resampling_actor: _ActorInfo | None = None
+        self._data_sourcing_actor: _ActorInfo[DataSourcingActor] | None = None
+        self._resampling_actor: _ActorInfo[
+            ComponentMetricsResamplingActor
+        ] | None = None
 
         self._battery_status_channel = Broadcast["BatteryStatus"](
             "battery-status", resend_latest=True