code: def dot(data, color=None, point_size=2, f_tooltip=None):
      
      from geoplotlib.layers import DotDensityLayer
      _global_config.layers.append(DotDensityLayer(data, color=color, point_size=point_size, f_tooltip=f_tooltip))
docs: 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