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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 get_model_abbrev(model_obj):
 """ Extract the string used to specify the model type of this model object in `pylogit.create_chohice_model`. Parameters model_obj : An MNDC_Model instance. Returns ------- str. The internal abbreviation used for the particular type of MNDC_Model. """

    # Get the 'display name' for our model.
    model_type = model_obj.model_type
    # Find the model abbreviation for this model's display name.
    for key in model_type_to_display_name:
        if model_type_to_display_name[key] == model_type:
            return key
    # If none of the strings in model_type_to_display_name matches our model
    # object, then raise an error.
    msg = "Model object has an unknown or incorrect model type."
    raise ValueError(msg)