There are no straight up examples. Best to run a policy to capture resources of what you are looking for and build a filter based upon what you find in the resources.json file. Below is some sample code to get you started along your path. Try running the custodian policy with no filter defined, just the resource then look at the resources.json contents..
- name: purge-lambda-after-7-days
- type: value
Example resources.json file;