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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_field_name(value):
 """Normalizing value string used as key and field name. :param value: String to normalize :type value: str :return: normalized string :rtype: str """

    # Replace non word/letter character
    return_value = re.sub(r'[^\w\s-]+', '', value)
    # Replaces whitespace with underscores
    return_value = re.sub(r'\s+', '_', return_value)
    return return_value.lower()