def __init__(self, data_type, default=None, **kwargs):
    """Constructor.

    Args:
      data_type: underlying data type as class.
      default: default value for the property. The value is deep copied
        fore each model instance.
      kwargs: remaining arguments.
    """
    kwargs["default"] = default
    super(JsonProperty, self).__init__(**kwargs)
    self.data_type = data_type
Constructor.

    Args:
      data_type: underlying data type as class.
      default: default value for the property. The value is deep copied
        fore each model instance.
      kwargs: remaining arguments.
    
mapreduce/model.py