Spell out Abstract Syntax Tree the first time it appears in the document.

Author: davepeck

peps/pep-0750.rst

@@ -339,13 +339,13 @@ in the output of the ``__iter__()`` method:
 .. code-block:: python
 
     first = "Eat"
-    second = "Roquefort"
+    second = "Red Leicester"
     template = t"{first}{second}"
     contents = list(template)
     assert len(contents) == 2
     assert contents[0].value == "Eat"
     assert contents[0].expression == "first"
-    assert contents[1].value == "Roquefort"
+    assert contents[1].value == "Red Leicester"
     assert contents[1].expression == "second"
 
     # However, the strings attribute contains empty strings:
@@ -833,9 +833,10 @@ in terms of formal grammars. Developers will need to learn how to work with the
 ``strings`` and ``interpolation`` attributes of a ``Template`` instance and how
 to process interpolations in a context-sensitive fashion. More sophisticated
 grammars will likely require parsing to intermediate representations like an
-AST. Great template processing code will handle format specifiers and conversions
-when appropriate. Writing production-grade template processing code -- for
-instance, to support HTML templates -- can be a large undertaking.
+abstract syntax tree (AST). Great template processing code will handle format
+specifiers and conversions when appropriate. Writing production-grade template
+processing code -- for instance, to support HTML templates -- can be a large
+undertaking.
 
 We expect that template strings will provide framework authors with a powerful
 new tool in their toolbox. While the functionality of template strings overlaps