Объект типа 'str' не вызывается, в чем проблема?

from selenium import webdriver
from selenium.webdriver.common.keys import Keys
import time

class instagramBot:
  def __init__(self, login, password):
    self.login = login
    self.password = password
    self.driver = webdriver.Firefox()

  def closeBrowser(self):
    self.driver.close()

  def login(self):
    driver = self.driver
    driver.get("https://www.instagram.com/")
    time.sleep(2)

IB = instagramBot("","")
IB.login()

Traceback (most recent call last):
  File "C:\Users\Max\Desktop\GetFollowersBot\getFollowers.py", line 20, in <module>
    IB.login()
TypeError: 'str' object is not callable

Process finished with exit code 1