[SPARK-32338][SQL][PYSPARK][FOLLOW-UP] Update slice to accept Column for start and length

### What changes were proposed in this pull request?

This is a follow-up of #29138 which added overload `slice` function to accept `Column` for `start` and `length` in Scala.

This PR is updating the equivalent Python function to accept `Column` as well.

### Why are the changes needed?

Now that Scala version accepts `Column`, Python version should also accept it.

### Does this PR introduce _any_ user-facing change?

Yes, PySpark users will also be able to pass Column object to `start` and `length` parameter in `slice` function.

### How was this patch tested?

Added tests.

Closes #29195 from ueshin/issues/SPARK-32338/slice.

Authored-by: Takuya UESHIN <ueshin@databricks.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>

python/pyspark/sql/functions.py

@@ -2068,7 +2068,11 @@ def slice(x, start, length):
     [Row(sliced=[2, 3]), Row(sliced=[5])]
     """
     sc = SparkContext._active_spark_context
-    return Column(sc._jvm.functions.slice(_to_java_column(x), start, length))
+    return Column(sc._jvm.functions.slice(
+        _to_java_column(x),
+        start._jc if isinstance(start, Column) else start,
+        length._jc if isinstance(length, Column) else length
+    ))
 
 
 @since(2.4)

python/pyspark/sql/tests/test_functions.py

@@ -292,6 +292,16 @@ class FunctionsTests(ReusedSQLTestCase):
         for result in results:
             self.assertEqual(result[0], '')
 
+    def test_slice(self):
+        from pyspark.sql.functions import slice, lit
+
+        df = self.spark.createDataFrame([([1, 2, 3],), ([4, 5],)], ['x'])
+
+        self.assertEquals(
+            df.select(slice(df.x, 2, 2).alias("sliced")).collect(),
+            df.select(slice(df.x, lit(2), lit(2)).alias("sliced")).collect(),
+        )
+
     def test_array_repeat(self):
         from pyspark.sql.functions import array_repeat, lit