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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def wait_for_login(self, timeout=90):
 """Waits for the QR to go away"""

        WebDriverWait(self.driver, timeout).until(
            EC.visibility_of_element_located((By.CSS_SELECTOR, self._SELECTORS['mainPage']))
        )