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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 _prepare_env(self):
 # pragma: no cover """Setup the document's environment, if necessary."""

        env = self.state.document.settings.env
        if not hasattr(env, self.directive_name):
            # Track places where we use this directive, so we can check for
            # outdated documents in the future.
            state = DirectiveState()
            setattr(env, self.directive_name, state)
        else:
            state = getattr(env, self.directive_name)
        return env, state