docs: update debugging_basic.rst with trainer var (#18856)

(cherry picked from commit 1ac49b1)

Author: rasbt

docs/source-pytorch/debug/debugging_basic.rst

@@ -51,13 +51,13 @@ The :paramref:`~lightning.pytorch.trainer.trainer.Trainer.fast_dev_run` argument
 
 .. code:: python
 
-    Trainer(fast_dev_run=True)
+    trainer = Trainer(fast_dev_run=True)
 
 To change how many batches to use, change the argument to an integer. Here we run 7 batches of each:
 
 .. code:: python
 
-    Trainer(fast_dev_run=7)
+    trainer = Trainer(fast_dev_run=7)
 
 
 .. note::
@@ -142,7 +142,7 @@ To turn off the autosummary use:
 
 .. code:: python
 
-    Trainer(enable_model_summary=False)
+    trainer = Trainer(enable_model_summary=False)
 
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