feat: add median() for window rolling

Author: sycai

bigframes/core/window/rolling.py

@@ -59,6 +59,9 @@ def sum(self):
 
     def mean(self):
         return self._apply_aggregate(agg_ops.mean_op)
+    
+    def median(self):
+        return self._apply_aggregate(agg_ops.median_op)
 
     def var(self):
         return self._apply_aggregate(agg_ops.var_op)

tests/system/small/test_window.py

@@ -175,6 +175,7 @@ def test_series_groupby_rolling_closed_param(rows_rolling_series, closed):
         pytest.param(lambda x: x.min(), id="min"),
         pytest.param(lambda x: x.max(), id="max"),
         pytest.param(lambda x: x.mean(), id="mean"),
+        pytest.param(lambda x: x.median(), id="median"),
         pytest.param(lambda x: x.count(), id="count"),
         pytest.param(lambda x: x.std(), id="std"),
         pytest.param(lambda x: x.var(), id="var"),
@@ -210,6 +211,7 @@ def test_series_window_agg_ops(rows_rolling_series, windowing, agg_op):
         pytest.param(lambda x: x.min(), id="min"),
         pytest.param(lambda x: x.max(), id="max"),
         pytest.param(lambda x: x.mean(), id="mean"),
+        pytest.param(lambda x: x.median(), id="median"),
         pytest.param(lambda x: x.count(), id="count"),
         pytest.param(lambda x: x.std(), id="std"),
         pytest.param(lambda x: x.var(), id="var"),

third_party/bigframes_vendored/pandas/core/window/rolling.py

@@ -21,6 +21,10 @@ def sum(self):
     def mean(self):
         """Calculate the weighted window mean."""
         raise NotImplementedError(constants.ABSTRACT_METHOD_ERROR_MESSAGE)
+    
+    def median(self):
+        """Calculate the rolling median."""
+        raise NotImplementedError(constants.ABSTRACT_METHOD_ERROR_MESSAGE)
 
     def var(self):
         """Calculate the weighted window variance."""