module API
  module V1
    class PlaceResource < JSONAPI::Resource

      attributes :name, :place_type, :geometry, :neighborhood_ids

      def place_type
        @model.type
      end

      def geometry
        @model.to_geojson
      end

      def neighborhood_ids
        return [] if @model.type == 'Neighborhood'
        @model.neighborhoods.pluck(:id)
      end

    end
  end
end

module API
  module V1
    class PlaceResource < JSONAPI::Resource

      attributes :name, :place_type, :geometry

      def place_type
        @model.type
      end

      def geometry
        @model.to_geojson
      end

    end
  end
end

--- 
+++ 
@@ -2,7 +2,7 @@
   module V1
     class PlaceResource < JSONAPI::Resource
 
-      attributes :name, :place_type, :geometry
+      attributes :name, :place_type, :geometry, :neighborhood_ids
 
       def place_type
         @model.type
@@ -12,6 +12,11 @@
         @model.to_geojson
       end
 
+      def neighborhood_ids
+        return [] if @model.type == 'Neighborhood'
+        @model.neighborhoods.pluck(:id)
+      end
+
     end
   end
 end
Add neighborhood id collection so frontend can query municipality and all its neighborhoods as a filter
