code: function isDataFile (filename) {
    const ext = path.extname(filename)
    const filenameWithoutExt = path.basename(filename, ext)
  
    return filenameWithoutExt === 'data' && ext === '.xml'
  }
docs: Is a file qualifying to be a data file? ie. `data.xml`. We don't check the content here, just the name.