title: How to check a valid csv file?
body: <p>I have a csv file in this format</p>
  
  <pre><code>"emails"
  "foo.bar@foo.com"
  "bar.foo@foo.com"
  "foobar@foo.com"
  </code></pre>
  
  <p>If a file is not in the above format, I want to throw a file format error. How to do this?</p>