chore(init-templates): Python app template imports 'core' as 'cdk' to align sample code across languages (#12970)

For consistency and to make it easier to translate TypeScript examples into Python, import the `aws_cdk.core` module as `cdk`.

There are snippets in the CDK Developer Guide that assume the `core` module is imported as `core`. It is difficult to synchronize changes to the CDK with changes in the Guide, so this PR causes the `core` module to be imported under _both_ names. Once this change is released, the Guide snippets can be updated to use `cdk` rather than `core` to refer to the `core` module. At some point in the future, this template can be updated again to remove the now-redundant `core` import.

This is to support this Guide issue: awsdocs/aws-cdk-guide#268 which intends to make all code snippets in the Guide follow the guidance in the "Working with the CDK in Python" topic.

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: Jerry Kindall

packages/aws-cdk/lib/init-templates/v1/app/python/%name.PythonModule%/%name.PythonModule%_stack.template.py

@@ -1,9 +1,15 @@
+from aws_cdk import core as cdk
+
+# For consistency with other languages, `cdk` is the preferred import name for
+# the CDK's core module.  The following line also imports it as `core` for use
+# with examples from the CDK Developer's Guide, which are in the process of
+# being updated to use `cdk`.  You may delete this import if you don't need it.
 from aws_cdk import core
 
 
-class %name.PascalCased%Stack(core.Stack):
+class %name.PascalCased%Stack(cdk.Stack):
 
-    def __init__(self, scope: core.Construct, construct_id: str, **kwargs) -> None:
+    def __init__(self, scope: cdk.Construct, construct_id: str, **kwargs) -> None:
         super().__init__(scope, construct_id, **kwargs)
 
         # The code that defines your stack goes here

packages/aws-cdk/lib/init-templates/v1/app/python/app.template.py

@@ -1,11 +1,17 @@
 #!/usr/bin/env python3
 
+from aws_cdk import core as cdk
+
+# For consistency with TypeScript code, `cdk` is the preferred import name for
+# the CDK's core module.  The following line also imports it as `core` for use
+# with examples from the CDK Developer's Guide, which are in the process of
+# being updated to use `cdk`.  You may delete this import if you don't need it.
 from aws_cdk import core
 
 from %name.PythonModule%.%name.PythonModule%_stack import %name.PascalCased%Stack
 
 
-app = core.App()
+app = cdk.App()
 %name.PascalCased%Stack(app, "%name.StackName%")
 
 app.synth()