How to remove the gap behind the tail of an arrow created with plotly.py's add_annotation()?

I am using the plotly.graph_objects.Figure.add_annotation() function to add an arrow into my plot - see a simple example code below:

import plotly.graph_objects as go

fig = go.Figure()

fig.add_annotation(ax = 3, axref = 'x', ay = 2, ayref = 'y',
                   x = 4, xref = 'x', y = 2, yref = 'y',
                   arrowhead = 3)

fig.add_shape(x0 = 1, x1 = 3, xref = 'x',
              y0 = 1, y1 = 3, yref = 'y')

fig.add_shape(x0 = 4, x1 = 6, xref = 'x',
              y0 = 1, y1 = 3, yref = 'y')

fig.update_layout(xaxis_range = [0, 7], yaxis_range = [0, 4])

fig.show()

which renders the following image:

As you can see, there is a small gap between the left rectangle and the tail of the arrow. Is there a way to remove this gap, so that the arrow starts exactly as specified by the parameters ax and ay ? I have tried looking through the documentation to see if there may be other relevant parameters of the add_annotation() function but couldn’t find clues. Thanks!

Answered on SO.