Printing /Saving a plot as a png file with alpha transparency issue

[RT]

Printing / saving a plot as a png file with an alpha channel issue

I tried

https://stackoverflow.com/questions/12438777/saving-a-plot-in-octave-with-transparent-background

set(gcf, 'Position',  [10, 10, 500, 500]);
print(gcf,'-dpngalpha', 'myplot.png');

I get an error 
error: print: unknown device pngalpha
error: called from
    __print_parse_opts__ at line 265 column 5
    print at line 316 column 8

I'm using Octave 4.2.2

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