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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 _createWorkingDir(rootdir,input):
 """ Create a working directory based on input name under the parent directory specified as rootdir """

    # extract rootname from input
    rootname = input[:input.find('_')]
    newdir = os.path.join(rootdir,rootname)
    if not os.path.exists(newdir):
        os.mkdir(newdir)
    return newdir