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Mapbox line layers. are not seen in the legend section

Hi,

I created mapbox line layers. But they are not seen in the legend section.
What am I missing ?

regards

here is the code snippet:

mapBoxlayout = Layout(
width=1400,
height=800,

    autosize=True,
    hovermode='closest',
    showlegend = True ,
    mapbox=dict(
        accesstoken=mapbox_access_token,
        bearing=0,
        center=dict(
            lat=38.8,
            lon=36
        ),
        pitch=0,
        zoom=5,

        layers=[
            dict(
                sourcetype = 'geojson',
                source = geojson_layer1,
                type = 'line',
                color = 'rgba(255,0,0,0.6)',
                line = dict(width=4)
            ),
            dict(
                sourcetype = 'geojson',
                source = geojson_layer2,
                type = 'line',
                color = 'rgba(33,113,181,0.6)',
                line = dict(width=2)
            ),
            dict(
                sourcetype = 'geojson',
                source = geojson_layer34,
                type = 'line',
                color = 'rgba(0,0,0,0.4)',
                line = dict(width=1)
            )
        ]
    ),

)