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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 _init(self, style, streamer, processors=None):
 """Do writer-specific setup. Parameters style : dict Style, as passed to __init__. streamer : interface.Stream A stream interface that takes __init__'s `stream` and `interactive` arguments into account. processors : field.StyleProcessors, optional A writer-specific processors instance. Defaults to field.PlainProcessors(). """

        self._stream = streamer
        if streamer.interactive:
            if streamer.supports_updates:
                self.mode = "update"
            else:
                self.mode = "incremental"
        else:
            self.mode = "final"

        if style and "width_" not in style and self._stream.width:
            style["width_"] = self._stream.width
        self._content = ContentWithSummary(
            StyleFields(style, processors or PlainProcessors()))