Add sample for ast extraction.

python/samples/ast_extraction.py

@@ -0,0 +1,17 @@
+#  Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+#  See https://llvm.org/LICENSE.txt for license information.
+#  SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+from npcomp.compiler.frontend import *
+
+def binary_expression():
+  a = 1
+  b = 100
+  c = a * b + 4
+  return c
+
+fe = ImportFrontend()
+try:
+  f = fe.import_global_function(binary_expression)
+finally:
+  print(fe.ir_module.to_asm(debug_info=True))