@Nullable
      @Override
      public Object recurse(List<Object> location, String target) {
         final int value = parseUnsignedInt(target);
         if (value == INVALID_INT) {
            return null;
         }
         if (value >= location.size()) {
            return null;
         }
         return location.get(value);
      }
Mapper for handling populating the query variables with the files specified by object paths
in the multi-part request.
graphql-protocol/src/main/java/com/linecorp/armeria/server/graphql/protocol/MultipartVariableMapper.java