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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 instantiate_references_json(references_json):
    ''' Given a JSON representation of all the models in a graph, return a
    dict of new model objects.

    Args:
        references_json (``JSON``)
            JSON specifying new Bokeh models to create

    Returns:
        dict[str, Model]

    '''

    # Create all instances, but without setting their props
    references = {}
    for obj in references_json:
        obj_id = obj['id']
        obj_type = obj.get('subtype', obj['type'])

        cls = get_class(obj_type)
        instance = cls.__new__(cls, id=obj_id)
        if instance is None:
            raise RuntimeError('Error loading model from JSON (type: %s, id: %s)' % (obj_type, obj_id))
        references[instance.id] = instance

    return references