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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 _updateFilename(self):
 """Calls several methods after the filename changed. This method is also a `SLOT`. It checks the encoding of the changed filename and generates a preview of the data. """

        self._filename = self._filenameLineEdit.text()
        self._guessEncoding(self._filename)
        self._previewFile()