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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 sign_in(self, email, password):
 """Signs in using the specified email address and password."""

        self.email = email
        self.login_password = password
        if self.is_element_present(*self._next_button_locator):
            self.wait.until(expected.visibility_of_element_located(
                self._next_button_locator))
            self.click_next()
        self.click_sign_in()