class ActiveSupport::Cache::Store

def namespaced_key(key, options)

with a colon.
Prefix a key with the namespace. Namespace and key will be delimited

def namespaced_key(key, options)
  key = expanded_key(key)
  namespace = options[:namespace] if options
  prefix = namespace.is_a?(Proc) ? namespace.call : namespace
  key = "#{prefix}:#{key}" if prefix
  key
end