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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 _run_first(self, source_file):
 """Run on as first in chain."""


        self.reset()
        self.current_encoding = self.default_encoding
        encoding = None
        try:
            encoding = self._detect_encoding(source_file)
            content = self.filter(source_file, encoding)
        except UnicodeDecodeError:
            if not encoding or encoding != self.default_encoding:
                content = self.filter(source_file, self.default_encoding)
            else:
                raise
        return content