nested

# File actionpack/lib/action_dispatch/routing/mapper.rb, line 1385
        def nested
          unless resource_scope?
            raise ArgumentError, "can't use nested outside resource(s) scope"
          end

          with_scope_level(:nested) do
            if shallow? && shallow_nesting_depth >= 1
              shallow_scope(parent_resource.nested_scope, nested_options) { yield }
            else
              scope(parent_resource.nested_scope, nested_options) { yield }
            end
          end
        end