ListType serialize_when_none=False doesn't seem to work

[trutia]

One of the fields in our model is ListType and is being set to None if though it is not being passed in.

[tirkarthi]

Can you please attach a sample script to explain the current and expected behavior? I am trying out the below where serialize_when_none when set to True has the field in serialized value. When set to False doesn't have the field in the serialized value.

from schematics.models import Model
from schematics.types import StringType, ListType


class ModelB(Model):
    field1 = ListType(StringType(), serialize_when_none=True)
    field2 = ListType(StringType(), serialize_when_none=False)


model = ModelB()
print(model.serialize())

python samplelistnone.py
{'field1': None}