Confusing behaviour of VariantRecord.filter

[awgymer]

Trying to check the filter values of a record:

chr1	882644	MY_DEL	T	<DEL>	35	.	END=882732

print(record.filter.items())
[]

'PASS' in record.filter
True

'PASS' in record.filter.keys()
False

The behaviour of this in check feels confusing.
Is it correct and expected that the right way to check if a particular record has a filter value is by using keys?

I am guessing that doing in on just record.filter is checking the header associated with this record (which obviously has the PASS row)?