`Argument type is partially unknown` for a union of date/time patterns

[goncalossilva]

I have a field whose type is:

MyDate = Union[DatePattern["%F"], DateTimePattern["%FT%T"], UTCDateTimePattern["%FT%TZ"]]

@dataclass
class Due(JSONPyWizard):
	date: MyDate

(see #189 for why this isn't using the union syntax!)

Pyright flags attempts to access this field (e.g., a simple print statement) with:

Argument type is partially unknown
  Argument corresponds to parameter "values" in function "print"
  Argument type is "DatePattern[Unknown] | DateTimePattern[Unknown] | UTCDateTimePattern[Unknown]"