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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 _deserialize(self, value, attr, data):
 """Deserialize sanitized string value."""

        value = super(SanitizedUnicode, self)._deserialize(value, attr, data)
        value = fix_text(value)

        # NOTE: This `join` might be ineffiecient... There's a solution with a
        # large compiled regex lying around, but needs a lot of tweaking.
        value = ''.join(filter(self.is_valid_xml_char, value))
        for char in self.UNWANTED_CHARACTERS:
            value = value.replace(char, '')
        return value