Correct and expand comment regarding trace.run_xxx

And one other comment in trace_fn_call_event

mathics/core/builtin.py

@@ -8,16 +8,20 @@
 
 import importlib
 import re
-from functools import lru_cache, total_ordering
+from functools import total_ordering
 from itertools import chain
 from typing import Any, Callable, Dict, Iterable, List, Optional, Tuple, Union, cast
 
 import mpmath
 import sympy
 
-# Note: it is important *not* use: from mathics.eval.tracing import run_sympy
-# but instead import the module and access below as tracing.run_sympy.
-# This allows us change where tracing.run_sympy points at runtime.
+# Note: it is important *not* to use:
+#   from mathics.eval.tracing import run_sympy
+# but, instead, import the module, as below, and then
+# access ``run_sympy`` using ``tracing.run_sympy.``
+#
+# This allows us to change where ``tracing.run_sympy`` points to at
+# run time.
 import mathics.eval.tracing as tracing
 from mathics.core.atoms import (
     Integer,

mathics/eval/tracing.py

@@ -18,7 +18,7 @@
 
 def trace_fn_call_event(func: Callable) -> Callable:
     """
-    Wrap a a call event with callbacks
+    Wrap a call event with callbacks,
     so we can track what happened before the call and
     the result returned by the call.