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Plot latitude and longitude points, change the size of the dots depending on third variable

I am plotting latitude and longitude on a scattermapbox using the following code:

dcc.Graph(
    id='map',
    figure={
		'data': [{
		    'lat': df2['lat'],
		    'lon': df2['lon'],
		    'type': 'scattermapbox',
		    #'selectedpoints': selected_indices,
		    'selected': {
		        'marker': {'color': '#85144b'}
		    }
		}],
		'layout': {
		    'mapbox': {
		        'center': {
		            'lat': 52.89,
		           'lon': -1.83
		        },
		        'zoom': 5,
		        'accesstoken': 'pk.eyJ1IjoiY2hyaWRkeXAiLCJhIjoiY2oyY2M4YW55MDF1YjMzbzhmemIzb290NiJ9.sT6pncHLXLgytVEj21q43A'
		    },
		    'margin': {'l': 0, 'r': 0, 't': 0, 'b': 0}
		}
    }
),

I want to make the size of the dots depend on a third variable. That seems to be quite easy to do in plotly but the same syntax doesn’t work in dash. How would I go about doing this?