Uploading packages to nexus3 using python script

I am using the following code to upload a sample file to nexus repository. I found this on one of the answers

import requests
from requests.auth import HTTPBasicAuth

url ='https://localhost:8081/nexus/service/rest/v1/components'

params = (
   ('repository', 'tools'),
)

payload = {
    'maven2.groupId': (None, 'com.example'),
    'maven2.artifactId': (None, 'test-app'),
    'maven2.version': (None, '1.0.4'),
    'maven2.asset1': ('example.json', open('example.json', 'rb')),
    'maven2.asset1.extension': (None, 'json'),
}
try:
    response = requests.post(url,
                             params=params,
                             files=payload
                             )
    response.raise_for_status()
except requests.exceptions.HTTPError as errh:
    print("Http Error:", errh)
    exit(1)
except requests.exceptions.ConnectionError as errc:
    print("Error Connecting:", errc)
    exit(1)
except requests.exceptions.Timeout as errt:
    print("Timeout Error:", errt)
    exit(1)
except requests.exceptions.RequestException as err:
    print("OOps: Something Else", err)
    exit(1)

I would like to know what is the speciality of None in the line 'maven2.groupId': (None, 'com.example')

Please excuse me if this question does not fit here. But could you clarify