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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 _is_method_retryable(self, method):
 """ Checks if a given HTTP method should be retried upon, depending if it is included on the method whitelist. """

        if self.method_whitelist and method.upper() not in self.method_whitelist:
            return False

        return True