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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 user_exists(self, username):
 """Determines if the user exists. Args: username: The user name. Returns: bool: True if the user exists in the Crowd application. """


        response = self._get(self.rest_url + "/user",
                             params={"username": username})

        if not response.ok:
            return None

        return True