'Get the model class for the kind.
Args:
kind: A string representing the name of the kind to lookup.
default_model: The model class to use if the kind can\'t be found.
Returns:
The model class for the requested kind.
Raises:
KindError: The kind was not found and no default_model was provided.'

@classmethod
def _lookup_model(cls, kind, default_model=None):

    modelclass = cls._kind_map.get(kind, default_model)
    if (modelclass is None):
        raise KindError(("No    model    class    found    for    kind    '%s'.    Did    you    forget    to    import    it?" % kind))
    return modelclass
