code: function transform({ babel, filename, documentFilename }) {
    if (!filename) {
      throw new Error(
        `You must pass a filename to importMDX(). Please see the mdx.macro documentation`,
      )
    }
    let documentPath = path.join(filename, '..', documentFilename);
    let imports = `import React from 'react'\nimport { MDXTag } from '@mdx-js/tag'\n`
  
    // In development mode, we want to import the original document so that
    // changes will be picked up and cause a re-build.
    // Note: this relies on files with macros *not* being cached by babel.
    if (process.env.NODE_ENV === "development") {
      imports += `import '${documentPath}'\n`
    }
  
    let source = fs.readFileSync(documentPath, 'utf8');
    let transformedSource =
      babel.transformSync(
        imports+mdx.sync(source),
        {
          presets: [babelPresetReactApp],
          filename: documentPath,
        },
      ).code
  
    return writeTempFile(documentPath, transformedSource)
  }
docs: Find the import filename,