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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 _find_hstreaming():
 """Finds the whole path to the hadoop streaming jar. If the environmental var HADOOP_HOME is specified, then start the search from there. Returns: Full path to the hadoop streaming jar if found, else return an empty string. """

    global WARNED_HADOOP_HOME, HADOOP_STREAMING_PATH_CACHE
    if HADOOP_STREAMING_PATH_CACHE:
        return HADOOP_STREAMING_PATH_CACHE
    try:
        search_root = os.environ['HADOOP_HOME']
    except KeyError:
        search_root = '/'
    cmd = 'find %s -name hadoop*streaming*.jar' % (search_root)
    p = subprocess.Popen(cmd.split(), stdout=subprocess.PIPE,
                         stderr=subprocess.PIPE)
    HADOOP_STREAMING_PATH_CACHE = p.communicate()[0].split('\n')[0]
    if search_root == '/' and not WARNED_HADOOP_HOME:
        WARNED_HADOOP_HOME = True
        hadoop_home = HADOOP_STREAMING_PATH_CACHE[:HADOOP_STREAMING_PATH_CACHE.rfind('/contrib/')]
        logging.warn('Set the HADOOP_HOME environmental variable to your hadoop path to improve performance. Put the following [export HADOOP_HOME="%s"] in ~/.bashrc' % hadoop_home)
    return HADOOP_STREAMING_PATH_CACHE