error when writing to file

[roiDaniela]

Hello,

I built a graph and trying to write png but getting the folowing error:
'charmap' codec can't encode character '\u03bb' in position 27: character maps to

versions:
windows 10
python 3.8
pydot 1.4.2

graph:
digraph G {
rankdir=LR;
"λ" [fillcolor="#66cc33", peripheries=2, style=filled];
ba [peripheries=2];
baa [peripheries=2];
baba [peripheries=2];
b;
bab;
"λ" -> b [label=b];
ba -> baa [label=a];
ba -> bab [label=b];
b -> ba [label=a];
bab -> baba [label=a];
}

Thanks