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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 decode(cls, line):
 """ Remove backslash escaping from line.valueDecode line, either to remove backslash espacing, or to decode base64 encoding. The content line should contain a ENCODING=b for base64 encoding, but Apple Addressbook seems to export a singleton parameter of 'BASE64', which does not match the 3.0 vCard spec. If we encouter that, then we transform the parameter to ENCODING=b """

        if line.encoded:
            if 'BASE64' in line.singletonparams:
                line.singletonparams.remove('BASE64')
                line.encoding_param = cls.base64string
            encoding = getattr(line, 'encoding_param', None)
            if encoding:
                line.value = codecs.decode(line.value.encode("utf-8"), "base64")
            else:
                line.value = stringToTextValues(line.value)[0]
            line.encoded=False