src/language-js/embed.js/hasLanguageComment
function hasLanguageComment(node, languageName) {
  // This checks for a leading comment that is exactly `/* GraphQL */`
  // In order to be in line with other implementations of this comment tag
  // we will not trim the comment value and we will expect exactly one space on
  // either side of the GraphQL string
  // Also see ./clean.js
  return hasLeadingComment(
    node,
    (comment) =>
      isBlockComment(comment) && comment.value === ` ${languageName} `
  );
}