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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 get_num_nodes(properties=None, hadoop_conf_dir=None, offline=False):
 """ Get the number of task trackers in the Hadoop cluster. All arguments are passed to :func:`get_task_trackers`. """

    return len(get_task_trackers(properties, hadoop_conf_dir, offline))