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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 sign(self, authenticator):
 		"""Sign this OMAPI message. 		@type authenticator: OmapiAuthenticatorBase 		"""

		self.authid = authenticator.authid
		self.signature = b"\0" * authenticator.authlen  # provide authlen
		self.signature = authenticator.sign(self.as_string(forsigning=True))
		assert len(self.signature) == authenticator.authlen