'Serialize the model `item` to a dictionary.
Given model `item` and the list `keys`, create and return a dictionary
built from each key in `keys` that also exists in `serializers` and
values of calling the keyed/named serializers on item.'

def serialize(self, item, keys, **context):

    returned = {}
    for key in keys:
        if (key in self.serializers):
            try:
                returned[key] = self.serializers[key](item, key, **context)
            except SkipAttribute:
                pass
        elif (key in self.serializable_keyset):
            returned[key] = self.default_serializer(item, key, **context)
    return returned
