Expose ResamplingFunction and SourceProperties

`ResamplingFunction` is used by `ResamplerConfig`, which is public, and
`SourceProperties` is used by `ResamplingFunction`, so both should be
public too.

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

Author: llucax

src/frequenz/sdk/timeseries/__init__.py

@@ -40,7 +40,8 @@
 from ._fuse import Fuse
 from ._moving_window import MovingWindow
 from ._periodic_feature_extractor import PeriodicFeatureExtractor
-from ._resampling._config import ResamplerConfig
+from ._resampling._base_types import SourceProperties
+from ._resampling._config import ResamplerConfig, ResamplingFunction
 
 __all__ = [
     "Bounds",
@@ -49,7 +50,9 @@
     "PeriodicFeatureExtractor",
     "ResamplerConfig",
     "ReceiverFetcher",
+    "ResamplingFunction",
     "Sample",
     "Sample3Phase",
+    "SourceProperties",
     "UNIX_EPOCH",
 ]