Steps to reproduce:

1. Container memory discovery is working, but the Prometheus to JSON parameter filters out all the results - thus no item prototypes are delivered.
2. Prometheus to JSON contains the following:

   container_memory_cache\{container =~ ".*", namespace =~ ".*", pod =~ "POD"}
   

   Result:

    No item prototypes are created for any running pods on the system

Expected:
    I believe the intent may have been to filter accordingly:

     container_memory_cache\{container !~ "POD", namespace =~ ".*", pod =~ ".*"}

After updating the discovery rule's preprocessing steps to the above I can see all the expected output in the results.