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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 start(self, activity, action):
        '''
        Mark an action as started

        :param activity: The virtualenv activity name
        :type  activity: ``str``

        :param action: The virtualenv action
        :type  action: :class:`tox.session.Action`
        '''
        try:
            self._start_action(activity, action)
        except ValueError:
            retox_log.debug("Could not find action %s in env %s" % (activity, self.name))
        self.refresh()