LLMGraphTransformer Invalid schema for response_format 'extract'

[platkevicius]

public async addDocument(document: Document[], apikey: string) {
    this.logger.debug("Started saving of documents");
    const graphStore = await this.getGraphStore();
    const graphTransformer = await this.getGraphTransformer(apikey);
    try {
      const result = await graphTransformer.convertToGraphDocuments(document);
      this.logger.log(result);
    } catch (error) {
      this.logger.error(
        "Failed converting documents to graph documents",
        error as Error,
      );
      throw error;
    }
  }

private async getGraphTransformer(apikey: string): Promise<LLMGraphTransformer> {
    const model = await this.modelService.getModelForApiKeyId(
      Model.GPT_4O,
      apikey,
    );

    return new LLMGraphTransformer({
      llm: model,
      nodeProperties: ["TOPIC", "CONCEPT"],
      relationshipProperties: ["RELATED_TO", "PART_OF"],
      strictMode: false,
    });
  }

Calling the method addDocument results in the following error message: Invalid schema for response_format 'extract': schema must be a JSON Schema of 'type: "object"', got 'type: "None"'. I just followed this documentation: https://js.langchain.com/docs/how_to/graph_constructing/