Is the Session object from Python's Requests library thread safe?

import grequests

s = requests.Session()

requests = [grequests.post("http://127.0.0.1:5000", 
                           data=json.dumps({'value': d}), session=s)
            for d in range(300)]

responses = grequests.map(requests)
for r in responses:
    if r.content.strip() != str(d*2):
        print("Sent %s got %s" % (r.content, str(d*2)))
    if r.status_code != 200:
        print(r.status_code)
        print(r.content)

s2.headers.update(headers)

import requests
url = "https://www.nseindia.com"
s2 = requests.session()
s2.headers.update({'User-Agent': 'Mozilla/5.0'})
s2_req = s2.get(url)
print("Session with header Cookies ", s2.cookies.keys())

Session with header Cookies  ['ak_bmsc']