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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 dispatch(self, **changes):
 """ Patch the swarm with changes and then trigger the swarm. """

        self.patch(**changes)
        trigger_url = self._vr._build_url(self.resource_uri, 'swarm/')
        resp = self._vr.session.post(trigger_url)
        resp.raise_for_status()
        try:
            return resp.json()
        except ValueError:
            return None