How to convert email as a blob in Gmail Addon Using Card Services

My aim to convert an email's content, with attachments, into a binary large object (blob) format within the Gmail add-on. I'm getting the body content using the below function but I'm not able to convert it into blob format.

I referred to the following documents but I don't know which function I have to use here for blob format.

1. Blob
2. GmailApp

function loadAddon(event){
    var accessToken = event.gmail.accessToken;
    var messageId = event.gmail.messageId;
    GmailApp.setCurrentMessageAccessToken(accessToken);
    var mailMessage = GmailApp.getMessageById(messageId);
    var emailContent = mailMessage.getBody();
    console.log("Email Content: " + emailContent);
}

Can anyone guide me on this?

In order to create a blob of the eml format, please modify the script as follows.

Modified script:

function loadAddon(event) {
  var accessToken = event.gmail.accessToken;
  var messageId = event.gmail.messageId;
  GmailApp.setCurrentMessageAccessToken(accessToken);
  var mailMessage = GmailApp.getMessageById(messageId);
  var emailContent = mailMessage.getBody();
  console.log("Email Content: " + emailContent);

  var blob = Utilities.newBlob(mailMessage.getRawContent(), "message/rfc822", "sampleFilename.eml");
}

• In this modification, a blob of eml format can be obtained by Utilities.newBlob(mailMessage.getRawContent(), "message/rfc822", "sampleFilename.eml").

Reference:

• newBlob(data, contentType, name)