How to - Select and Delete all Wall Types with Name Containing String

[Yna_Db]

Optionally, see what’s in the Primer, all basics are clearly explained there:
http://dynamoprimer.com/en/08_Dynamo-for-Revit/8-2_Selecting.html
Don’t hesitate to search with diverse keywords also:

Creating a List of Wall Types

I am trying to create a list of wall types that is just of the types not of the instances.

All elements

Families = loadable families, not system families. You can get all wall types using Element Type and All Elements of Type. And you can pass that list into Clockwork’s All Elements of Family Type+ to get all wall instances.