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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 update(self):
 """Get info from dataset before opening dialog."""

        self.filename = self.parent.info.dataset.filename

        self.chan = self.parent.info.dataset.header['chan_name']
        for chan in self.chan:
            self.idx_chan.addItem(chan)