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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 init_app(self, app, env_file=None, verbose_mode=False):
 """Imports .env file."""

        if self.app is None:
            self.app = app
        self.verbose_mode = verbose_mode

        if env_file is None:
            env_file = os.path.join(os.getcwd(), ".env")
        if not os.path.exists(env_file):
            warnings.warn("can't read {0} - it doesn't exist".format(env_file))
        else:
            self.__import_vars(env_file)