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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 _log_deprecation(self, deprecation_key):
 """ Logs a deprecation notice at most once per AgentCheck instance, for the pre-defined `deprecation_key` """

        if not self._deprecations[deprecation_key][0]:
            self.log.warning(self._deprecations[deprecation_key][1])
            self._deprecations[deprecation_key][0] = True