How to type in a textarea with selenium python?

I'm trying to comment on instagram with selenium just for testing, but I'm not able to type inside the textarea, follow the part of the code.

    comentar = driver.find_element_by_tag_name('textarea')
    comentar.clear()
    comentar.send_keys('Comentario')

I'm having to use it.

keyboard.type("@Fabiany_Hey")
keyboard.press(Key.enter)

But only type if the window is in focus.

The first code returns this error.

Traceback (most recent call last):
  File "C:\Users\Pichau\Desktop\Teste.py", line 24, in <module>
    comentar.send_keys('Comentario')
  File "C:\Users\Pichau\AppData\Local\Programs\Python\Python36-32\lib\site-packages\selenium\webdriver\remote\webelement.py", line 479, in send_keys
    'value': keys_to_typing(value)})
  File "C:\Users\Pichau\AppData\Local\Programs\Python\Python36-32\lib\site-packages\selenium\webdriver\remote\webelement.py", line 628, in _execute
    return self._parent.execute(command, params)
  File "C:\Users\Pichau\AppData\Local\Programs\Python\Python36-32\lib\site-packages\selenium\webdriver\remote\webdriver.py", line 312, in execute
    self.error_handler.check_response(response)
  File "C:\Users\Pichau\AppData\Local\Programs\Python\Python36-32\lib\site-packages\selenium\webdriver\remote\errorhandler.py", line 242, in check_response
    raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.StaleElementReferenceException: Message: stale element reference: element is not attached to the page document
  (Session info: chrome=66.0.3359.139)
  (Driver info: chromedriver=2.38.552522 (437e6fbedfa8762dec75e2c5b3ddb86763dc9dcb),platform=Windows NT 10.0.16299 x86_64)

HTML:

<textarea aria-label="Adicione um comentário..." placeholder="Adicione um comentário..." class="_bilrf" autocomplete="off" autocorrect="off"></textarea>

I'm using python 3.6