Transparency (Alpha) in hl.plot.scatter


I am looking to add an alpha parameter to the hl.plot.scatter function.
I have PCAs plotted with the scatter function, with many samples (4000+), so I would like to see the overlapping points. Bokeh has an alpha function but this needs to be specified when the circles are plotted, and can’t be adjusted in the plot returned from the scatter function.

Is there a way to specify the alpha, or can this be a parameter added to the scatter plot?