Update PR template

Author: nikhilym

.github/PULL_REQUEST_TEMPLATE.md

@@ -2,5 +2,22 @@
 Since these model classes are auto-generated using the [JSON schemas](https://developer.amazon.com/docs/custom-skills/request-and-response-json-reference.html) 
 in the developer documentation, we do not currently accept Pull Requests.
 
-All Pull Requests will be automatically closed. 
-!-->
+All Pull Requests will be automatically closed, unless the request is generic and applies across **ALL** model classes.
+!-->
+## Description
+<!--- Describe your changes in detail -->
+
+## Testing
+<!--- Please describe in detail how you tested your changes -->
+<!--- Include details of your testing environment like python version, dependencies,  -->
+<!--- and the tests you ran to see how your change affects other areas of the code, etc. -->
+
+## Motivation and Context
+<!--- Why is this change required? What problem does it solve? -->
+<!--- If it fixes an open [issue][issues], please link to the issue here -->
+
+## Checklist
+- [ ] My code follows the code style of this project
+- [ ] My change requires a change to the documentation
+- [ ] The change is generic and can be done across all model classes.
+- [ ] By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.