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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 _lookup_model(cls, kind, default_model=None):
 """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. """

    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