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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def model_node(**kwargs):
 """ Decorates a ``schematics.Model`` class to add it as a field of type ``schematic.types.ModelType``. Keyword arguments are passed to ``schematic.types.ModelType``. Example: .. code-block:: python :emphasize-lines: 8,13 from schematics import Model, types from rafter.contrib.schematics.helpers import model_node class MyModel(Model):
 name = types.StringType() @model_node() class options(Model):
 status = types.IntType() # With arguments and another name @model_node(serialized_name='extra', required=True) class _extra(Model):
 test = types.StringType() """

    kwargs.setdefault('default', {})

    def decorator(model):
        return types.ModelType(model, **kwargs)

    return decorator