如何在盖茨比上使用getNodesByType？

Question

创建页面后，我想使用getNodesByType来查看 节点存储中存在的内容。但我不知道如何使用。

这个

const markdownNodes = getNodesByType（MarkdownRemark）

blog.js

    import React from 'react';
    import { graphql } from 'gatsby';
    import Layout from '../components/layout';
    import Nav from '../components/nav';
    import SEO from '../components/seo';
    import Iframely from '../components/Iframely';
    import './blog.css';
    
    const BlogTemplate = (props) => {
        return (
            <Layout>
            <SEO title={props.data.contentfulBlog.seoTitle} description={props.data.contentfulBlog.seoDesriptcion} keywords={props.data.contentfulBlog.seoKeywords} />
            <Iframely />
            <Nav />
            <div className='blog__header'>
                <div className='blog__hero' style={{backgroundImage:  `url(${props.data.contentfulBlog.featuredImage.fluid.src})`}}></div>
                <div className='blog__info'>
                    <h1 className='blog__title'>{props.data.contentfulBlog.title}</h1>
                </div>
            </div>
            <div className='blog__wrapper'>
                <div className='blog__content'>
                    <div dangerouslySetInnerHTML={
                        {__html: `${props.data.contentfulBlog.content.childMarkdownRemark.html}`}
                    } />
                </div>
            </div>
            </Layout>
        )
    }
    
    export default BlogTemplate;
    

export const query = graphql`
 query BlogTemplate($id: String!) {
    contentfulBlog(id: {eq: $id}) {
     title
     id
     slug
     content {
       childMarkdownRemark {
         html
       }
     }
    seoTitle
    seoDescription
    seoAuthor
    seoKeywords

  
     seoImage {
       fluid(maxWidth: 1200, quality: 100) {
         ...GatsbyContentfulFluid
         src
       }
     }
     featuredImage {
       fluid(maxWidth: 1200, quality: 100) {
         ...GatsbyContentfulFluid
         src
       }
     }
   }
 }
`