Retrieves the token from the File System
        :return dict or None: The token if exists, None otherwise

def get_token(self):
        """
        Retrieves the token from the File System
        :return dict or None: The token if exists, None otherwise
        """
        token = None
        if self.token_path.exists():
            with self.token_path.open('r') as token_file:
                token = self.token_constructor(self.serializer.load(token_file))
        self.token = token
        return token