How to add a file as a base64 string when sending a document for signature?

curl -X 'POST' \
  'https://api.boldsign.com/v1/document/send' \
  -H 'accept: application/json' \
  -H 'X-API-KEY:{Your API Key}' \
  -H 'Content-Type: application/json' \
  -d '{
    "Message": "Please sign this.",
    "Signers": [
        {
            "name": "Alex",
            "emailAddress": "alexgayle@cubeflakes.com",
            "signerType": "Signer",
            "formFields": [
                {
                    "id": "sign1",
                    "name": "sign1",
                    "fieldType": "Signature",
                    "pageNumber": 1,
                    "bounds": {
                        "x": 50,
                        "y": 50,
                        "width": 125,
                        "height": 25
                    },
                    "isRequired": true
                }
              ],
            "locale": "EN"
        }
    ],
   
   "Files": [
        "data:application/pdf;base64,JVBERi0xLjcKJcfs..."
    ],
    "Title": "Agreement"
  }'
  

import requests
import json

url = "https://api.boldsign.com/v1/document/send"

signer_data = {
    "name": "Alex",
    "emailAddress": "alexgayle@cubeflakes.com",
    "signerType": "Signer",
    "formFields": [
        {
            "id": "sign1",
            "name": "sign1",
            "fieldType": "Signature",
            "pageNumber": 1,
            "bounds": {
                "x": 50,
                "y": 50,
                "width": 200,
                "height": 25
            },
            "isRequired": True
        }
       
    ],
    "locale": "EN"
}

payload = {
    'Message': 'Please sign this.',
    'Signers': [signer_data],
    'Title': 'Agreement',
    'Files': [
        'data:application/pdf;base64,JVBERi0xLjcNCi...'
    ]   
}

headers = {
  'Content-Type': 'application/json',
  'accept': 'application/json',
  'X-API-KEY': '{Your API Key}'
}

response = requests.post(url, headers=headers, json=payload)
print(response.text)

const axios = require('axios');

const url = "https://api.boldsign.com/v1/document/send";

const signerData = {
  "name": "Alex",
  "emailAddress": "alexgayle@cubeflakes.com",
  "signerType": "Signer",
  "formFields": [
    {
      "id": "string",
      "name": "string",
      "fieldType": "Signature",
      "pageNumber": 1,
      "bounds": {
        "x": 50,
        "y": 50,
        "width": 200,
        "height": 25
      },
      "isRequired": true
    }
  ],
  "locale": "EN"
};

const payload = {
  'Message': 'Please sign this.',
  'Signers': [signerData],
  'Title': 'Agreement',
  'Files': [
    'data:application/pdf;base64,JVBERi0xLjcNCi...'
  ]
};

const headers = {
  'Content-Type': 'application/json',
  'accept': 'application/json',
  'X-API-KEY': '{Your API Key}'
};

axios.post(url, payload, { headers })
  .then(response => {
    console.log(response.data);
  })
  .catch(error => {
    console.error('Error:', error);
  });