fix: fix error in Series.drop(0) (#575)

Due to implicit 0 non-truthfulness, 0 was getting erroneously converted to None.

Author: milkshakeiii

bigframes/series.py

@@ -351,9 +351,11 @@ def drop(
  columns: Union[blocks.Label, typing.Iterable[blocks.Label]] = None,
  level: typing.Optional[LevelType] = None,
  ) -> Series:
- if labels and index:
- raise ValueError("Must specify exacly one of 'labels' or 'index'")
- index = labels or index
+ if (labels is None) == (index is None):
+ raise ValueError("Must specify exactly one of 'labels' or 'index'")
+
+ if labels is not None:
+ index = labels
 
  # ignore axis, columns params
  block = self._block

tests/system/small/test_series.py

@@ -1529,10 +1529,16 @@ def test_groupby_window_ops(scalars_df_index, scalars_pandas_df_index, operator)
  )
 
 
-def test_drop_label(scalars_df_index, scalars_pandas_df_index):
- col_name = "int64_col"
- bf_series = scalars_df_index[col_name].drop(1).to_pandas()
- pd_series = scalars_pandas_df_index[col_name].drop(1)
+@pytest.mark.parametrize(
+ ("label", "col_name"),
+ [
+ (0, "bool_col"),
+ (1, "int64_col"),
+ ],
+)
+def test_drop_label(scalars_df_index, scalars_pandas_df_index, label, col_name):
+ bf_series = scalars_df_index[col_name].drop(label).to_pandas()
+ pd_series = scalars_pandas_df_index[col_name].drop(label)
  pd.testing.assert_series_equal(
  pd_series,
  bf_series,