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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 initialize_tracer(self, io_loop=None):
 """ Initialize Jaeger Tracer based on the passed `jaeger_client.Config`. Save it to `opentracing.tracer` global variable. Only the first call to this method has any effect. """


        with Config._initialized_lock:
            if Config._initialized:
                logger.warn('Jaeger tracer already initialized, skipping')
                return
            Config._initialized = True

        tracer = self.new_tracer(io_loop)

        self._initialize_global_tracer(tracer=tracer)
        return tracer