code: public MapAssert<String, Object> isObject() {
          Node node = assertType(OBJECT);
          return new JsonMapAssert((Map<String, Object>) node.getValue(), path.asPrefix(), configuration)
              .as("Different value found in node \"%s\"", path);
      }
docs: Asserts that given node is present and is of type object.
  
  @return MapAssert where the object is serialized as Map