Thanks @DexterLaBora for the tips.
import requests
fields_array = "fields[]=isManaged&fields[]=isSupervised"
network_ID = 'N_1234567890'
url = "https://api.meraki.com/api/v1/networks/{0}/sm/devices?{1}".format(network_ID, fields_array)
payload = None
headers = {
"Content-Type": "application/json",
"Accept": "application/json",
"X-Cisco-Meraki-API-Key": "9abcdefghijklmnopqrstuvzxyz"
}
response = requests.request('GET', url, headers=headers, data = payload)
print(response.text.encode('utf8'))