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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_base64(attr):
 """Deserialize base64 encoded string into string. :param str attr: response string to be deserialized. :rtype: bytearray :raises: TypeError if string format invalid. """

        if isinstance(attr, ET.Element):
            attr = attr.text
        padding = '=' * (3 - (len(attr) + 3) % 4)
        attr = attr + padding
        encoded = attr.replace('-', '+').replace('_', '/')
        return b64decode(encoded)