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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 sanitize(self, s):
 """sanitize a string for comparison. """

        if not isinstance(s, six.string_types):
            return s

        """
        re.sub matches a regex and replaces it with another.
        The regex replacements are taken from a file if the option
        is passed when py.test is called. Otherwise, the strings
        are not processed
        """
        for regex, replace in six.iteritems(self.parent.sanitize_patterns):
            s = re.sub(regex, replace, s)
        return s