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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_visualizations():
 """Get the available visualizations from the request context. Put the visualizations in the request context if they are not yet there. Returns: :obj:`list` of instances of :class:`.BaseVisualization` or derived class """

    if not hasattr(g, 'visualizations'):
        g.visualizations = {}
        for VisClass in _get_visualization_classes():
            vis = VisClass(get_model())
            g.visualizations[vis.__class__.__name__] = vis
    return g.visualizations