I am new to Stackoverflow, puppet and kubernetes as well.

I need to create an if conditional, to check if a certain label exist in the environment field for kubernetes label in Kibana Filters, using puppet and if it does not exist it will add it. This is what I have so far, and where reads ?? -is where I am not sure what goes there, I have tought about setting a regex,

if [kubernetes] {   
  if [kubernetes][labels][app_kubernetes_io\/environment] = ?? {
    mutate { add_field => { "environment" => [kubernetes][labels][app_kubernetes_io\/environment]  } }  
}