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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 raise_for_status(self):
        '''Raise Postmark-specific HTTP errors. If there isn't one, the
        standard HTTP error is raised.

        HTTP 401 raises :class:`UnauthorizedError`

        HTTP 422 raises :class:`UnprocessableEntityError`

        HTTP 500 raises :class:`InternalServerError`
        '''
        if self.status_code == 401:
            raise UnauthorizedError(self._requests_response)
        elif self.status_code == 422:
            raise UnprocessableEntityError(self._requests_response)
        elif self.status_code == 500:
            raise InternalServerError(self._requests_response)
        return self._requests_response.raise_for_status()