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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 disable_tracing_hostname(url, blacklist_hostnames=None):
 """Disable tracing for the provided blacklist URLs, by default not tracing the exporter url. If the url path starts with the blacklisted path, return True. :type blacklist_hostnames: list :param blacklist_hostnames: URL that not tracing. :rtype: bool :returns: True if not tracing, False if tracing. """

    if blacklist_hostnames is None:
        # Exporter host_name are not traced by default
        _tracer = execution_context.get_opencensus_tracer()
        try:
            blacklist_hostnames = [
                '{}:{}'.format(
                    _tracer.exporter.host_name,
                    _tracer.exporter.port
                )
            ]
        except(AttributeError):
            blacklist_hostnames = []

    return url in blacklist_hostnames