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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 _truncate_wildcard_from_date(date_value):
 """Truncate wildcard from date parts. Returns: (str) The truncated date. Raises: ValueError, on either unsupported date separator (currently only ' ' and '-' are supported), or if there's a wildcard in the year. Notes: Either whole date part is wildcard, in which we ignore it and do a range query on the remaining parts, or some numbers are wildcards, where again, we ignore this part. """

    if ' ' in date_value:
        date_parts = date_value.split(' ')
    elif '-' in date_value:
        date_parts = date_value.split('-')
    else:
        # Either unsupported separators or wildcard in year, e.g. '201*'.
        raise ValueError("Erroneous date value: %s.", date_value)

    if GenericValue.WILDCARD_TOKEN in date_parts[-1]:
        del date_parts[-1]

    return '-'.join(date_parts)