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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, fields):
 """ Log the start message. The action identification fields, and any additional given fields, will be logged. In general you shouldn't call this yourself, instead using a C{with} block or L{Action.finish}. """

        fields[ACTION_STATUS_FIELD] = STARTED_STATUS
        fields.update(self._identification)
        if self._serializers is None:
            serializer = None
        else:
            serializer = self._serializers.start
        Message(fields, serializer).write(self._logger, self)