Ignore unknown battery bucket in the absence of system bounds

If a proposal arrives for a previously unknown battery bucket, and
there are no system bounds available for the bucket, then ignore the
proposal.

This commit also improves the code comments for the case where a
previous target power already exists for a given battery bucket,
because in that case, we bring the target power down to zero.

Signed-off-by: Sahas Subramanian <[email protected]>

Author: shsms

src/frequenz/sdk/actor/_power_managing/_matryoshka.py

@@ -5,6 +5,7 @@
 
 from __future__ import annotations
 
+import logging
 import typing
 
 from typing_extensions import override
@@ -16,6 +17,8 @@
 if typing.TYPE_CHECKING:
     from ...timeseries.battery_pool import PowerMetrics
 
+_logger = logging.getLogger(__name__)
+
 
 class Matryoshka(BaseAlgorithm):
     """The matryoshka algorithm."""
@@ -49,6 +52,21 @@ def get_target_power(
                 already part of another bucket.
         """
         if battery_ids not in self._battery_buckets:
+            # if there are no previous proposals and there are no system bounds, then
+            # don't calculate a target power and just return `None`.
+            if (
+                system_bounds.inclusion_bounds is None
+                and system_bounds.exclusion_bounds is None
+            ):
+                if proposal is not None:
+                    _logger.warning(
+                        "PowerManagingActor: No system bounds available for battery "
+                        "IDs %s, but a proposal was given.  The proposal will be "
+                        "ignored.",
+                        battery_ids,
+                    )
+                return None
+
             for bucket in self._battery_buckets:
                 if any(battery_id in bucket for battery_id in battery_ids):
                     raise NotImplementedError(
@@ -68,7 +86,10 @@ def get_target_power(
         lower_bound = (
             system_bounds.inclusion_bounds.lower
             if system_bounds.inclusion_bounds
-            else Power.zero()  # in the absence of system bounds, block all requests.
+            # if a target power exists from a previous proposal, and the system bounds
+            # have become unavailable, force the target power to be zero, by narrowing
+            # the bounds to zero.
+            else Power.zero()
         )
         upper_bound = (
             system_bounds.inclusion_bounds.upper