Clarify Lazy API / Query plan

docs/src/python/user-guide/lazy/query_plan.py

@@ -9,6 +9,7 @@
     .with_columns(pl.col("name").str.to_uppercase())
     .filter(pl.col("comment_karma") > 0)
 )
+q1.show_graph(optimized=False)
 # --8<-- [end:plan]
 
 # --8<-- [start:createplan]

docs/user-guide/lazy/query_plan.md

@@ -11,17 +11,16 @@ We can understand both the non-optimized and optimized query plans with visualiz
 
 ### Graphviz visualization
 
-First we visualise the non-optimized plan by setting `optimized=False`.
-
-{{code_block('user-guide/lazy/query_plan','plan',['show_graph'])}}
-
 <div style="display:none">
 ```python exec="on" result="text" session="user-guide/lazy/query_plan"
 --8<-- "python/user-guide/lazy/query_plan.py:setup"
---8<-- "python/user-guide/lazy/query_plan.py:plan"
 ```
 </div>
 
+First we visualise the non-optimized plan by setting `optimized=False`.
+
+{{code_block('user-guide/lazy/query_plan','plan',['show_graph'])}}
+
 ```python exec="on" session="user-guide/lazy/query_plan"
 --8<-- "python/user-guide/lazy/query_plan.py:createplan"
 ```
@@ -36,7 +35,11 @@ The query plan visualisation should be read from bottom to top. In the visualisa
 
 We can also print the non-optimized plan with `explain(optimized=False)`
 
-{{code_block('user-guide/lazy/query_plan','plan',['explain'])}}
+{{code_block('user-guide/lazy/query_plan','describe',['explain'])}}
+
+```python exec="on" session="user-guide/lazy/query_plan"
+--8<-- "python/user-guide/lazy/query_plan.py:describe"
+```
 
 ```text
 FILTER [(col("comment_karma")) > (0)] FROM WITH_COLUMNS:
@@ -82,4 +85,4 @@ The optimized plan is to:
 - apply the filter on the `comment_karma` column while the CSV is being read line-by-line
 - transform the `name` column to uppercase
 
-In this case the query optimizer has identified that the `filter` can be applied while the CSV is read from disk rather than writing the whole file to disk and then applying it. This optimization is called *Predicate Pushdown*.
+In this case the query optimizer has identified that the `filter` can be applied while the CSV is read from disk rather than reading the whole file into memory and then applying the filter. This optimization is called *Predicate Pushdown*.