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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 set_placeholder(self, key, value):
 """Placeholders are custom magic variables defined during configuration time. .. note:: These are accessible, like any uWSGI option, in your application code via ``.runtime.environ.uwsgi_env.config``. :param str|unicode key: :param str|unicode value: """

        self._set('set-placeholder', '%s=%s' % (key, value), multi=True)

        return self