def _validate_reserved_words(slug, words=SYSTEM_FIELDS):
    if slug in words:
        return _('You may not use "{}" as a field name').format(slug)
    for prefix in [SYSTEM_PREFIX, 'xml']:
        if slug and slug.startswith(prefix):
            return _('Field names may not begin with "{}"').format(prefix)
dataset/ETHPy150Open dimagi/commcare-hq/corehq/apps/custom_data_fields/models.py/_validate_reserved_words/original