savedot: HTML labels no longer quoted.

When employing a HTML label on a vertex, savedot used to add additional double quotes. Upon processing the file, DOT then shows the literal HTML string instead of parsing it. This is corrected now.

Author: pierretotale

src/persistence.jl

@@ -37,7 +37,12 @@ function savedot(io::IO, g::AbstractMetaGraph)
         end
         for p in props(g, v)
             key = p[1]
-            write(io, "$key=\"$(p[2])\",")
+            if  key .=== :label && occursin(r"<+.*>+$", p[2])
+                # The label is an HTML string, no additional quotes here.
+                write(io, "$key=$(p[2]),")
+            else
+                write(io, "$key=\"$(p[2])\",")
+            end
         end
         if length(props(g, v)) > 0
             write(io, "];")