def METHOD_NAME(business: Business,  # pylint: disable=too-many-branches
            filing: Dict,
            filing_rec: Filing,
            filing_meta: FilingMeta,
            filing_event_data: Dict):  # pylint: disable=too-many-branches
    """Process the incoming historic conversion filing."""
    # Extract the filing information for incorporation
    filing_meta.conversion = {}
    if not (conversion_filing := filing.get('filing', {}).get('conversion')):
        print(f'CONVL legal_filing:conversion missing from {filing_rec.id}')
    if business and business.legal_type in ['SP', 'GP']:
        _process_firms_conversion(business, filing, filing_rec, filing_meta, filing_event_data)
    else:
        business = _process_corps_conversion(business, conversion_filing, filing, filing_rec)
    return business, filing_rec