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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 normalize_header(name, existing=[]):
 """ Try to emulate the way in which Google does normalization on the column names to transform them into headers. """

    name = re.sub('\W+', '', name, flags=re.UNICODE).lower()
    # TODO handle multiple columns with the same name.
    return name