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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 signable(self, request, authheaders, response_body):
 """Creates the signable string for a response and returns it. Keyword arguments: request -- A request object which can be consumed by this API. authheaders -- A string-indexable object which contains the headers appropriate for this signature version. response_body -- A string or bytes-like object which represents the body of the response. """

        nonce = authheaders["nonce"]
        timestamp = request.get_header("x-authorization-timestamp")
        try:
            body_str = response_body.decode('utf-8')
        except:
            body_str = response_body
        return '{0}\n{1}\n{2}'.format(nonce, timestamp, body_str)