Remove 'unknown' json fields

output.txt

JsonRecord(unknown_json_keys={'foo': 'bar'})
JsonRecord()

remove_fields.py

from normalize import JsonRecord
from normalize.visitor import VisitorPattern


class RemoveUnknownKeys(VisitorPattern):
    @classmethod
    def unpack(cls, value, t, v):
        if hasattr(value, "unknown_json_keys"):
            del value.unknown_json_keys
        return super(RemoveUnknownKeys, cls).unpack(value, t, v)

    @classmethod
    def apply(cls, *a):
        return None

    @classmethod
    def reduce(cls, *a):
        return None


jr = JsonRecord({"foo": "bar"})

print repr(jr)
RemoveUnknownKeys.visit(jr)
print repr(jr)