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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 _clean_text(self, text):
 """Performs invalid character removal and whitespace cleanup on text."""

        output = []
        for char in text:
            cp = ord(char)
            if cp in (0, 0xfffd) or self._is_control(char):
                continue
            if self._is_whitespace(char):
                output.append(' ')
            else:
                output.append(char)
        return ''.join(output)