Hello, QuantConnect community!

According to EDGAR filings, Apple's CUSIP is 037833100 (ends with 00).

This is confirmed in Fidelity:

7089_1638712756.jpg

But in `SecurityDefinitionSymbolResolverTests`, the CUSIP being tested is `03783310` (ends with 0).

When I bring up a research notebook, `03783310` works and 037833100 doesn't:

resolver = QuantConnect.Securities.SecurityDefinitionSymbolResolver()
print(resolver.CUSIP(cusip='037833100', tradingDate=datetime.date.today()))
> None
print(resolver.CUSIP(cusip='03783310', tradingDate=datetime.date.today()))
> AAPL

Is there some sort of CUSIP convention that I don't quite understand?