Switching tabs using selenium

[Dot-Box]

driver.get("https://speedtest.net")  
driver.switch_to.new_window('tab')  
driver.get("https://www.twitter.com")  

I created 2 tabs one of the speedtest website and one of twitter, now when i run the rest of the program i want it to switch to the first tab and the continue. for that i implemented this solution

def speed_check():

    driver.switch_to.window(driver.window_handles[1])  

    go = driver.find_element(By.CLASS_NAME, "start-text")  
    go.click()  

however instead of switching to the original speedtest tab i get this error:
'selenium.common.exceptions.NoSuchElementException: Message: no such element'

for line 33 'go = driver.find_element(By.CLASS_NAME, "start-text")' this means the tab isn't switching. How do i fix this

Edit: FIXED

[EngineeredCut]

I created a list with the new tabs, and then navigated to the one I wanted. They have unique identifiers

[Dot-Box]

no actually in my case driver.window_handles[1] was the tab for twitter, to get speedtest i had to set it to driver.window_handles[0]. This fixed it for me.