[BUG] Colons in the labels for relations of class diagrams return a syntax error

[justin-schema]

Describe the bug

The following line produces a syntax error when using a class diagram

Metrics --> Organization : "gist:isAbout"

To Reproduce

Expected behavior

The relation should be labelled as gist:isAbout

Screenshots

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context

I use this diagram type to make models of RDF graphs. It would be great if I can use the namespace prefixes with the appropriate syntax inside the labels to support reuse of these diagrams into making actual RDF