# File lib/hiera/backend.rb, line 16
      def lookup(key, scope, order_override, resolution_type, context)
        Hiera.debug("Using Hiera 1.x backend API to access instance of class #{@wrapped.class.name}. Lookup recursion will not be detected")
        value = @wrapped.lookup(key, scope, order_override, resolution_type.is_a?(Hash) ? :hash : resolution_type)

        # The most likely cause when an old backend returns nil is that the key was not found. In any case, it is
        # impossible to know the difference between that and a found nil. The throw here preserves the old behavior.
        throw (:no_such_key) if value.nil?
        value
      end