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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 authorization_header(self):
 """ Returns a string containing the authorization header used to authenticate with GenePattern. This string is included in the header of subsequent requests sent to GenePattern. """

        return 'Basic %s' % base64.b64encode(bytes(self.username + ':' + self.password, 'ascii')).decode('ascii')