line plotly with shaded area

import plotly.graph_objects as go

fig = go.Figure()
fig.add_trace(go.Scatter(x=[1, 2, 3, 4],
                         y=[0, 2, 3, 5],
                         fill='tozeroy')
             ) # fill down to xaxis
fig.update_layout(title='<b>Title</b>',
                  xaxis_title='<b>x</b>',
                  yaxis_title='<b>y</b>')
fig.show()