Requests gets no out put and no error

[water_fox]

using below, I am getting no error, but also no output....anyone able to help?

import requests
import json
import sys


def get_request(api_key):
    api_url='https://api.nasa.gov/planetary/apod'
    r= requests.get(api_url, headers = {"Content-Type": "application/json", "access_key": api_key})
    api_key ='<my api key>'

    print(r.content)
    get_request(api_key)