Upload one part and let the server assign its order for incremental sessions.

curl --request PUT \
  --url https://api.revoengine.com/api/v1/storage/uploads/{storageUploadSessionId}/parts \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "data": "aGVhZGVyMSxoZWFkZXIyCjEsMg=="
}
'

const options = {
  method: 'PUT',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({data: 'aGVhZGVyMSxoZWFkZXIyCjEsMg=='})
};

fetch('https://api.revoengine.com/api/v1/storage/uploads/{storageUploadSessionId}/parts', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://api.revoengine.com/api/v1/storage/uploads/{storageUploadSessionId}/parts"

payload = { "data": "aGVhZGVyMSxoZWFkZXIyCjEsMg==" }
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.put(url, json=payload, headers=headers)

print(response.text)