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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 dot(data, color=None, point_size=2, f_tooltip=None):
 """Create a dot density map :param data: data access object :param color: color :param point_size: point size :param f_tooltip: function to return a tooltip string for a point """

    from geoplotlib.layers import DotDensityLayer
    _global_config.layers.append(DotDensityLayer(data, color=color, point_size=point_size, f_tooltip=f_tooltip))