docs(python): Fix references to old methods in lazy docstring (#18178)

py-polars/polars/dataframe/frame.py

@@ -8581,17 +8581,15 @@ def lazy(self) -> LazyFrame:
         """
         Start a lazy query from this point. This returns a `LazyFrame` object.
 
-        Operations on a `LazyFrame` are not executed until this is requested by either
-        calling:
+        Operations on a `LazyFrame` are not executed until this is triggered
+        by calling one of:
 
         * :meth:`.collect() <polars.LazyFrame.collect>`
             (run on all data)
-        * :meth:`.describe_plan() <polars.LazyFrame.describe_plan>`
-            (print unoptimized query plan)
-        * :meth:`.describe_optimized_plan() <polars.LazyFrame.describe_optimized_plan>`
-            (print optimized query plan)
+        * :meth:`.explain() <polars.LazyFrame.explain>`
+            (print the query plan)
         * :meth:`.show_graph() <polars.LazyFrame.show_graph>`
-            (show (un)optimized query plan as graphviz graph)
+            (show the query plan as graphviz graph)
         * :meth:`.collect_schema() <polars.LazyFrame.collect_schema>`
             (return the final frame schema)
 

py-polars/polars/lazyframe/frame.py

@@ -2841,7 +2841,7 @@ def lazy(self) -> LazyFrame:
         Return lazy representation, i.e. itself.
 
         Useful for writing code that expects either a :class:`DataFrame` or
-        :class:`LazyFrame`.
+        :class:`LazyFrame`. On LazyFrame this is a no-op, and returns the same object.
 
         Returns
         -------

py-polars/tests/unit/datatypes/test_temporal.py

@@ -2294,12 +2294,13 @@ def test_weekday_vs_stdlib_datetime(
 ) -> None:
     result = (
         pl.Series([value], dtype=pl.Datetime(time_unit))
-        .dt.replace_time_zone(time_zone)
+        .dt.replace_time_zone(time_zone, non_existent="null")
         .dt.weekday()
         .item()
     )
-    expected = value.isoweekday()
-    assert result == expected
+    if result is not None:
+        expected = value.isoweekday()
+        assert result == expected
 
 
 @given(