class Shoulda::Matchers::ActionController::PermitMatcher::ParametersDoubleRegistry

def permitted_parameter_names(args = {})
  subparameter_name = args.fetch(:for, TOP_LEVEL)
  if double_collections_by_parameter_name.key?(subparameter_name)
    self.class.permitted_parameter_names_within(
      double_collections_by_parameter_name[subparameter_name]
    )
  else
    []
  end
end