Argument of type "Literal['']" cannot be assigned to parameter "default" of type "NoValue" in function "str"
"Literal['']" is incompatible with "NoValue"PylancereportGeneralTypeIssues

I believe this would be fixed by changing the methods definitions to Union types.
def str(self, var, default: Union(NoValue, str) = NOTSET, multiline=False):