No working link syntax in plugin diagrams

Grav 1.5.1 and diagrams plugin 1.0.3.

I'm not able to provide a working link syntax. Following example provides a diagram but link target is wrong:

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[mermaid]
graph TD
st{<a href=''http://google.com''>Gogle</a> test}
[/mermaid]

Is inserting a link somehow limited in plugin implementation?
TIA.