Add a nice str representation for Sample

Easier to read & compare, especially when debugging.

Signed-off-by: Mathias L. Baumann <[email protected]>

Author: Marenz

src/frequenz/sdk/timeseries/_base_types.py

@@ -34,6 +34,10 @@ class Sample(Generic[QuantityT]):
     value: QuantityT | None = None
     """The value of this sample."""
 
+    def __str__(self) -> str:
+        """Return a string representation of the sample."""
+        return f"Sample({str(self.timestamp)}, {str(self.value)})"
+
 
 @dataclass(frozen=True)
 class Sample3Phase(Generic[QuantityT]):