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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 _validate_apns_certificate(self, certfile):
 		"""Validate the APNS certificate at startup."""


		try:
			with open(certfile, "r") as f:
				content = f.read()
				check_apns_certificate(content)
		except Exception as e:
			raise ImproperlyConfigured(
				"The APNS certificate file at %r is not readable: %s" % (certfile, e)
			)