How to post a Json with a base64 file using python request?

Question

Right now I am programming an API with python, and I have the following problem: I have to POST the following JSON to an url:

prescription = {
"Name": “file_name", # This is a string
"Body" : "xxx",# (File in base64 format)
"ParentId" : "xxxxxxxxxxxxxxxxxx", # This is a string
"ContentType" : "xxxxx/xxx" # This is a string
}

But when I try to do the following request:

requests.post(url, prescription)

I am getting the following error:

TypeError: Object of type bytes is not JSON serializable

How can I make a request for posting that JSON? Is it even possible?

Thanks for your help.

EDIT: Using

"Body" : "xxx.decode("utf-8")"

worked, thanks for the help